Van Riemsdyk scored twice to power the Toronto Maple Leafs past the Sabres 3-1 in Ron Rolston's first game as an NHL head coach.
Rolston, who until Wednesday was the head coach of the AHL's Rochester Americans, was hired as the Sabres' interim coach following the club's decision to fire Lindy Ruff. Ruff, who also played 10 seasons for Buffalo, had been behind the club's bench since 1997 and was the NHL's longest-tenured head coach.
Prior to arriving in Rochester, Rolston spent seven seasons as a head coach with USA Hockey's national program, leading the under-18 squad to three gold medals and a silver in four world championship appearances.
Van Riemsdyk played for Rolston for two years, earning a world championship gold medal in 2006 before getting silver the following year.
"He's a big reason for the success I've been able to have as a hockey player," van Riemsdyk said. "He really kind of instilled that confidence and trust that he had in me as a player and he put me out there in pretty much every situation in every game and allowed me to grow.
"There was obviously some growing pains my first year, but the second year I was able to blossom under his tutelage and I feel thankful for everything he taught me."
But Rolston could only watch as the Sabres dropped their third straight and fifth of their past six games.
"I thought we played well in parts of the game," Rolston said. "I didn't like our second period, obviously it was the turning point.
"We had too many turnovers, we were forcing things, long shifts in the defensive zone. It was the difference."
Toronto erased a 1-0, first-period deficit with two goals in the second.
"The second period wasn't good enough," said Sabres goalie Ryan Miller, who turned aside 33 shots. "We stopped doing some things we did early in the game and it caught up with us."
Van Riemsdyk's power-play goal at 14:28 of the third -- his team-leading 11th -- gave Toronto breathing room after Miller stopped him with a glove save earlier on the power play.
Maple Leafs coach Randy Carlyle said van Riemsdyk's work away from the puck was a big reason for his success.
"He probably skated as strong in this hockey game as any game he has this year," Carlyle said. "It's good to see him move his feet and be rewarded.
"I think if he continues to skate and move his feet the way he did tonight, I don't think he shouldn't continue to score if he's going to stay around the net and go into those tough areas.
"He's going to continue to play with our top-six grouping of forwards and he's going to maintain power play time, all of those things should indicate he can continue to make contributions. It's all up to him."
Tyler Ennis scored for Buffalo.
Buffalo outshot Toronto 13-10 in the first period and also had the period's lone goal. Ennis scored his sixth of the season with a high wrist shot to Scrivens' blocker side at 13:20.
"You just try to get on a roll and stop as many pucks as possible," Scrivens said of his stop on Vanek. "Obviously I was fortunate he wasn't able to get the rebound up on me, but I gave myself an opportunity to make the save.
"Maybe a little bit of both hard work by me and unfortunate luck on his part."
Phaneuf's one-timer with four seconds remaining on a power play at 1:15 of the second tied it. The goal was the 100th of Phaneuf's NHL career.
Van Riemsdyk put Toronto ahead 2-1 at 18:04, converting a nifty 2-on-1 break with Phil Kessel as the Leafs outshot Buffalo 15-6.
"We didn't start very well. ... we got our skating game going in the second," Carlyle said. "And once we can get on that forecheck and continue to throw that puck in and come at teams in waves, we can be an effective team grinding teams down."
"That's what we felt the case was tonight because we didn't skate very well and were fortunate to get out of the first period with the score what it was."
NBA slam dunk champion Terrence Ross of the Toronto Raptors took in the game. ... Toronto wore its third sweater for the fourth of eight games this season. ... Toronto entered the game leading the NHL in hits (476) and fighting majors (20). ... The Sabres and Leafs will meet once more this season, March 21 in Buffalo. ... Rolston has been Rochester's head coach since the 2011-12 season, having compiled a 63-44-17 record.