BUFFALO, N.Y. -- Following a frustrating performance Saturday -- and an off-ice chat with his head coach -- Pittsburgh Penguins defenseman Kris Letang rebounded in a big way.

Letang had three assists to lead the Penguins to a 4-3 win over the Buffalo Sabres on Sunday afternoon. The bounce-back performance came after a disappointing display in a 4-2 loss to the Tampa Bay Lightning one day earlier.

"It was good to respond to that and have a good game, especially after yesterday," Letang said.

Right winger Patric Hornqvist, left winger Scott Wilson, right winger Phil Kessel and center Matt Cullen scored for the Penguins (30-20-8). Goalie Marc-Andre Fleury made 24 saves.

Letang was instrumental in helping Pittsburgh open up a 3-1 lead in the second period with two tremendous assists. Letang found Wilson to the right of the Sabres net 5:28 into the second to make it 2-1 and fed Kessel late in the second period on a terrific cross-ice pass.

It was in stark contrast to Saturday afternoon. Against Tampa Bay, Letang capped a frustrating evening with a double minor penalty for unsportsmanlike conduct and using an opposing player's stick after his own stick was slashed out of his hands. That prompted a talk with head coach Mike Sullivan about using his emotions in the right fashion.

"He's obviously an important player for us," Sullivan said. "He logs a lot of minutes. He's such a good player when he plays the game the right way and when he has control over his emotions. I love the fact that he's a passionate guy. He's a competitive guy. He really cares. That's why he's emotional but I love that about him, and that's what I told him. But obviously he's got to channel it the right way and I thought he did that."

Defenseman Zach Bogosian and right winger Brian Gionta scored for the Sabres (24-29-7). Goalie Robin Lehner made 27 saves.

"They kind of took over," Lehner said. "They're a good team over there. I think if we just kept doing what we were doing in the first period ... maybe we wouldn't have lost it there in the second."

The bad news continued for the Sabres after the game when head coach Dan Bylsma confirmed that leading scorer Ryan O'Reilly will miss 3-4 weeks due to a lower-body injury. O'Reilly was injured in Buffalo's 4-0 win over Columbus on Friday night.

"He's your No. 1 guy and that's something you can't replace," Bylsma said. "Where we're at right now in the season, had points in eight of 10 before tonight's game and winning some hockey games. He's a huge part of that."

Hornqvist opened the scoring 8:09 into the first period off a deflection. Hornqvist redirected defenseman Trevor Daley's shot inside the right post for his 12th goal of the year.

Bogosian evened the score with 6:12 remaining in the first. The defenseman blasted a one-timer from deep in the Penguins zone for his second goal of the year.

Wilson made it 2-1 5:28 into the second period moments after a questionable cross-checking penalty by Sabres center Jack Eichel turned a Sabres' power play into a 4-on-4 opportunity. Letang found Wilson wide open to the right of the Sabres' net with a cross-ice pass and Wilson lifted a high shot into the top of the net for his third goal of the year. All of Wilson's goals have come in the last three games.

Kessel made it 3-1 with 2:10 remaining in the second after another great pass by Letang and another Sabres defensive breakdown. With Kessel stationed to the left of the Sabres net, Letang fed a long cross-ice pass from behind the right circle. With a wide-open net and no Sabres nearby, Kessel easily scored his 19th goal of the season.

Cullen made it 4-1 7:52 into the third on a short-handed breakaway. Lehner initially stopped Cullen's wrist shot but the puck eventually trickled through the goaltender's pads and into the net.

Gionta got one back for the Sabres 13 seconds later off a deflection. Gionta tipped Bogosian's shot from the point to make it 4-2 at 8:05.

After pulling Lehner, Bogosian made it 4-3 with 21.4 seconds remaining on a long shot through traffic.

NOTES: C Ryan O'Reilly (lower body), D Carlo Colaiacovo and D Cody Franson (upper body) were scratched for the Sabres. O'Reilly and Franson were injured in Buffalo's 4-0 win over the Columbus Blue Jackets on Friday. With 49 points (17 goals, 32 assists), O'Reilly is Buffalo's top scorer. ... With O'Reilly out, the Sabres recalled RW Justin Bailey from the AHL's Rochester Americans. ... D Ben Lovejoy, LW Sergei Plotnikov and G Jeff Zatkoff were scratched for the Penguins. ... This was the second meeting between the two teams this season. Their third and final meeting takes place on March 29 in Pittsburgh.