NEW YORK -- The best 48 hours I've experienced at the world's wildest tennis tournament ended in a back corridor of an exclusive locker room that I never imagined having the license to enter.

"Sorry, Coach," Benjamin Becker told me.

"I should have served better. I had to serve better."

Becker was exactly right, of course, speaking strictly in terms of his objective Tuesday at the US Open, which was trying to shock the world -- as he did precisely a decade earlier -- by beating sixth-seeded Kei Nishikori in the first round.

Yet this was equally true about a conversation that was only possible in a players-and-coaches-only clubhouse because of the magical credential Becker improbably chose to hang around my neck:

The man who famously ushered Andre Agassi into retirement at the 2006 Open, having granted me unprecedented access to a world I've fantasized about since I was 13, was the last person on Earth who had to explain anything to me.

Thanks to Benni's benevolence, this tennis junkie just recharged for his 24th successive season of NBA coverage with a two-day fantasy camp straight off the Stein Line Bucket List.

Thanks to Becker, for the rest of my life now, I'll be able to answer the following question with the biggest smile:

How does it feel to go anywhere you want to go on the grounds of the National Tennis Center with a big gear bag slung over your shoulder in hopes that it makes you look like you know what you're doing?

Answer: Even better than you'd think.

I am by no means remotely qualified to coach a professional tennis player, even for a day, but that didn't stop Becker -- unexpectedly coachless at this Open -- from handing me the assignment. We've built a friendship as co-residents of the Dallas area over the past few years, sparked mostly by his and fellow German touring pro Philipp Petzschner's uber fandom of countryman Dirk Nowitzki and the NBA. The effect was doubled by my corresponding obsession with tennis, which began for me around the seventh grade and, truth be told, clinched my career choice of sports writer before I could drive.

So ...

Not knowing how many more Opens are in his future at 35 -- but knowing it would absolutely make my year to be summoned to Flushing Meadows -- Becker hatched the idea for me to join him and wife Kristin and attend as his, um, strategist.

Even if that really just meant me offering the loudest possible support while wearing a fancier badge than usual.

"I want to put you down as my coach," Becker wrote me after the Rio Olympics. "You'll have to fill out a form, I think, but I can choose anyone to be my coach. You just have to coach for real!"

Uh-oh.

Turns out there was no formal quiz I had to pass, but me being neurotic me, I couldn't help myself.

In truth, I'm fairly sure the last thing Benni wanted or needed before playing the former world No. 4 in a new stadium in the year's final major of an up-and-down season was me bombarding him with amateur input on how to attack Nishikori. Yet I was convinced I had to ‎do something to earn my keep. Or at least try to. So I did the only thing that made sense to a lifelong reporter.

I reported.

I reached out to every real coach/tour expert I could find in search of job advice and, more importantly, potential vulnerabilities in Nishikori's game/health/mental state that #TeamBenni could possibly exploit.

"You didn't pick the right opponent," ESPN's Chris Fowler offered, "to begin your coaching career."

Said Israel's Davis Cup captain Eyal Ran: "I suggest you drink a good coffee before the match. It won't influence the score, but it will make you feel better. Then make sure you take a trip to the restroom right before the match. You can't leave for even one minute once it starts; your player needs to see you every time he looks into the crowd."

On the strategy front, finally, came some good input from Golden State Warriors superfan Brad Gilbert, who years ago used to coach Nishikori: "To me, believe it or not, one place I would investigate is [hitting] deep down the middle. Sometimes Nishikori ... I think he's a lot better when he's one or two steps away from the center. I think Benni can make a little progression if he plays down the middle."

Big news in Flushing. Becker tells me that the great @ESPNSteinLine is coaching him this week. Career change, Stein? https://t.co/vq5w4D6LrU

— Josh Meiseles (@jmeistennis) August 30, 2016

Gilbert's theory was backed by Aussie innovator Craig O'Shannessy, who sits at the forefront of the movement to bring tennis into the modern age of sports analytics and starred on the first tennis panel in the history of the Sloan Sports Conference, which I moderated in the spring of 2012.

According to O'Shannessy's data, Becker's best shot at winning depended on keeping points short, keeping the ball away from Nishikori's backhand as much as he could and attacking as aggressively as possible on Nishikori's second serve.

A hint of competency bubbled inside me Tuesday morning when Becker informed me that he had largely arrived at the same conclusions in his own fact-finding quest before the match.

Then I started to feel borderline optimistic when, on top of the fact that two of the pair's five previous meetings went to a tiebreaker in the deciding set, Nishikori didn't show for his scheduled 9:15 a.m. warm-up on the gleaming new Grandstand court.

Blessed with a locked-in start time of 11 a.m. in the first match of the day, both camps naturally requested a practice hit to get a taste of the court. But because Benni also wanted to warm up in the 9 o'clock hour, which would have necessitated splitting the court, Nishikori's decision to scrap that planned session suggested, at least to me, that perhaps we had annoyed him a bit.

If so, it wasn't nearly enough annoyance. Nishikori fans started finding their way into the stands as early as 9:35 a.m. ... and their hero started just as quickly. The US Open's 2014 runner-up capitalized on two Benni double-faults in the opening game, crushed four winners for a second quick break and ultimately hit 13 outright winners to Benni's one in the opening set.

Coaching me through this trauma in the players' box was my dear friend and Dallas neighbor Philip Farmer, who helped Bob and Mike Bryan achieve their first year-end No. 1 ranking in doubles in 2003 and later worked with top singles stars Sam Querrey and Shahar Pe'er. He quickly spotted Benni's struggles to read where Nishikori was going with his expertly disguised backhand and tried his best to ease the blame I was inevitably heaping on myself for the 6-1, 6-1 hole that engulfed Becker after just 49 minutes on the court.

"This guy [Nishikori] off the ground," Dr. Phil tried to tell me, "is very powerful and very accurate."

But things changed dramatically in the third set. I'd love to be able to claim some responsibility, too, but it was all Benni. He called for a bathroom break and informed me after the match that there were no bathroom duties involved. With a USTA official waiting outside, Becker kicked the door as hard as he could, cursed himself out in German and purged a good bit of his boiling anger.

Wow the veteran Benny Becker has climbed off the canvas vs Special K after getting crushed 1st 2sets, props to new coach @ESPNSteinLine

— Brad Gilbert (@bgtennisnation) August 30, 2016

Then he started to play the shots he intended to from the start, hitting out on numerous forehands, leaning into his backhand and putting pressure on the Nishikori second serve. He won the third set in 41 minutes, seized an early break in the fourth and had me fist-pumping next to Dr. Phil in the box as if I thought it could truly make a difference.

Benni later told me that the only other time he had uncorked the door-kicking bathroom routine was the 2015 Australian Open, where he rallied from two sets down to stun Aussie legend Lleyton Hewitt in five sets. With Nishikori starting to look a bit shaky, I really believed we were, at worst, going to lose in five sets here. Benni had seized the momentum.

Or so I prematurely concluded.

At 2-1 up in the fourth set, Benni double-faulted three times, which understandably unnerved a big server like him. He would ultimately total an uncharacteristic 10 double faults, which is why he was so dismayed with his serving overall.

Just as costly was a missed overhead at 30-all in the seventh game of the set. If Benni converted there, he'd have seized a huge break point opportunity. But he netted the inviting smash and won only two more points thereafter before Nishikori closed out a 6-1, 6-1, 3-6, 6-3 triumph.

"I was excited about that overhead," Benni said. "I wanted him to hit the lob. I was so excited that I jumped too early and realized in the air that I jumped too early."

We spent a good 20 minutes after the match replaying it all in that locker room, player and coach, reconstructing dozens of points behind a solitary door that shuts out the rest of the tennis world. You can safely presume that I'll remember the whole experience with far greater fondness than Benni will, since I'll surely never get this close to the game again.

Chauffeured to the site of the Open at 8 a.m. in one of those snazzy silver Mercedes SUVs. Soaking up all the oxygen on the pristine Grandstand court with Benni and hitting partner Daniel Brands before anyone else set foot inside the stadium. Coaching head-to-head, if you want to get technical, against a rather famous fellow Orange County, California, native named Michael Chang.

It all made me feel close enough to where I surely could have convinced even 13-year-old Marc Stein that, at least for a couple of days, I really did make it behind the curtain.

What Benjamin Becker didn't know when he extended this short-term job offer is that this would also be a historic Open for me. I probably shouldn't be sticking this in the same paragraph as Benni's unforgettable triumph in '06, which led to one of the longest standing ovations in the game's history to bring Agassi's career to an emotional halt, but 2016 marks the 30th anniversary of my first trip here, when I attended this one-of-a-kind carnival on cement as a 17-year-old with my El Toro High School doubles partner Craig DiFilippo.

In those days, I still deluded myself into thinking I could emulate my heroes: Shlomo Glickstein and Amos Mansdorf. Two short years later, when I covered another one of my all-time faves -- John McEnroe -- in my first pro tournament as a tennis scribe on the campus of UCLA in September 1988, I was focused on becoming the next Bud Collins.

This coaching stuff was a sensational racket, too, especially for a lifelong tennis dreamer. But a return to the real world beckons.

When another NBA-loving tennis pal, former world No. 7 and Minnesota Timberwolves devotee Mardy Fish, checked in via text Tuesday afternoon to ask what went wrong for "Coach Steiny," I gave it to him straight.

Time to go back where I belong. Back to what I do best. Back to being a professional second-guesser on the other side of the door.