Bryan Rust scored, and Sidney Crosby had an assist to push his point streak to eight games for the Penguins (29-33-11), who have lost three of their past four (1-2-1) and remained six points behind the Montreal Canadiens, who have three games in hand, for the second wild card into the Stanley Cup Playoffs from the Eastern Conference.
Tristan Jarry allowed four goals on seven shots in the first period before being replaced by Alex Nedeljkovic, who made 18 saves.
"We just didn't play well enough," Pittsburgh coach Mike Sullivan said. "Most of the first (period) ... I don't think it was all that bad, but it just seemed like every chance went in the net. Just one of those nights."
Cirelli gave Tampa Bay a 1-0 lead at 12:13 of the first. He turned and scored from the low slot after Nick Paul’s redirection hit him in front.
"We didn't like our last two games on the road trip,” Cirelli said, referring to a 6-4 loss at the Utah Hockey Club on Saturday and a 4-2 loss at the Vegas Golden Knights on Sunday. “We wanted to come strong and play a complete 60-minute game. We wanted to establish the forecheck early and keep it simple."
McDonagh made it 2-0 at 13:30 when he sent the puck to the net from the left side and had it deflect in off the skate of Pittsburgh forward Rickard Rakell.
"We didn't have our strongest game today," Rakell said. "They just skated right through the neutral zone and played with possession the whole time. It felt like we were chasing the game from the start. Very disappointing."
Cirelli extended the lead to 3-0 at 15:12 with a wrist shot from the left face-off circle that beat Jarry to the short side.
"He's really grown as a player and he's been rewarded with Stanley Cups and he was a big part of that," Tampa Bay coach Jon Cooper said of Cirelli. "I think another unique reward was making the (Canada) 4 Nations (Face-Off) team and having the impact there that he did. Tony plays every shift like it's his last and that hard work has paid off."
Brayden Point made it 4-0 at 16:00 when he scored on the rebound of a Jake Guentzel shot, chasing Jarry.
Kucherov’s power-play goal made it 5-0 at 15:31 of the second period. He scored with a wrist shot from the left circle that beat Nedeljkovic to the stick side.
Hagel pushed it to 6-0 at 19:19 when he tapped in the puck from the doorstep off a pass from Nick Perbix.
"I think maybe our defensive game slipped from us a little bit. That's something we needed to get back on track with," Hagel said. "We did a good job of that tonight and we've just got to build off of it."
Rust cut it to 6-1 at 14:15 of the third period. Crosby had the secondary assist to give him 13 points (seven goals, six assists) during his point streak.
Crosby, who has 79 points (25 goals, 54 assists), is one point away from securing his 20th point-per-game season, which would pass Wayne Gretzky for the most in NHL history.
"We gave up some early ones that gave them momentum and it's tough to climb back from that deficit," said Crosby, the Penguins captain. "Just quick hits, a couple of rush plays. It didn't feel like they were carrying the play with zone time or putting us back on our heels. We weren't tight off the rush and they made us pay."
Penguins forward Evgeni Malkin was a late scratch with an upper-body injury. Sullivan said he was being evaluated further.
NOTES: Lightning defenseman Erik Cernak (undisclosed) left the game at 13:26 of the first and did not return. There was no update. ... Kucherov became the 10th player in NHL history to have three consecutive seasons with 70 or more assists. ... Point has three goals in the past three games. ... Rust has six points (four goals, two assists) during a three-game point streak.
