SAN JOSE, Calif. -- The Pittsburgh Penguins are speeding closer to their fourth Stanley Cup.

Pittsburgh's suffocating pace stifled the San Jose Sharks again Monday in a 3-1 win in Game 4 of the Stanley Cup finals at SAP Center. The Penguins pushed their advantage to 3-1 in the best-of-seven series.

"This is the hardest hockey I've witnessed in all the years I've been in this league," Penguins coach Mike Sullivan said. "You've got to work for every inch of ice."

Game 5 will be Thursday in Pittsburgh, where the Sharks have to win to force another game at home.

"This group doesn't get too frustrated. We just have to keep going," Sharks forward Chris Tierney said.

San Jose coach Peter DeBoer continued to shuffle personnel on his forward lines in hopes of finding combinations to solve the Penguins' defense. The fact the Sharks went 0-for-2 on the power play hurt, and Pittsburgh scored the first goal for a fourth consecutive game.

"When you have the lead, you can play differently and feel more comfortable getting into a four-line rhythm," DeBoer said. "You can put your guys out there, trust them, because there's not that pressure we have to create a chance and score a goal."

"I don't know what it is. It hasn't been an issue until this series, but it's been a big issue through four games," he added.

Melker Karlsson snapped Pittsburgh goalie Matt Murray's shutout bid with his fourth goal of the playoffs at 8:07 of the third period. He picked up a rebound of Brenden Dillon's blocked shot and beat Murray over his left glove to slice the Penguins' advantage to 2-1.

However, Pittsburgh's fourth-line right winger, Eric Fehr, scored his third goal of the playoffs at 17:58 for the insurance the Penguins needed to kill the hosts' comeback hopes.

"We've earned an opportunity, and that's it," Pittsburgh forward Matt Cullen said. "We haven't done anything yet, and it's easy to get far ahead of yourself."

Murray finished with 23 saves, while San Jose goalie Martin Jones made 17 stops.

Pittsburgh scored the only goal of the middle period to take a 2-0 lead into the third period.

Evgeni Malkin recorded his first goal of the series and fifth of the playoffs at 2:37, just nine seconds into Karlsson's interference penalty.

Malkin had an easy tap-in as he got slipped behind the Sharks defense on the far post, where teammate Phil Kessel hit him with a perfect cross-ice feed from above the left circle.

"Malkin's overall game was really good, at both ends of rink," Sullivan said. "(He's) so hard to defend. The puck follows him. It's one of his strongest games."

As has been the case throughout the series, Pittsburgh jumped out first and led 1-0 at the first intermission. The Sharks produced the final six shots to end a period with more shots than the Penguins for the first time (8-6).

"We've got to get the first goal. It's huge," Tierney said. "We're good when we have the lead, and they're good when they have the lead."

Sharks defenseman Paul Martin added, "That's been tough for us to claw and produce when we don't get that first one."

The Penguins took advantage of a bad San Jose line change to score 7:36 after the opening faceoff.

A quick turnaround shot by Kessel from the right circle bounded off Jones' pad right to an unmarked Ian Cole, and the Penguins defenseman one-timed his first goal of the playoffs past the San Jose netminder.

Jones made a number of key saves to keep it only a one-goal lead. Defenseman Brian Dumoulin was stoned on his second grade-A chance of the period at 11:30. And Jones denied both Penguins power-play shots after defenseman Marc-Edouard Vlasic interfered with Sidney Crosby at 11:37.

DeBoer started to shuffle his lines and shorten his bench at midgame.

Couture joined Joe Thornton and Joe Pavelski as he did late in Game 3. Centers Tierney and Nick Spaling were promoted one line each as forwards Karlsson, Dainius Zubrus and Tommy Wingels saw their ice time reduced in the second period.

In the third, Joonas Donskoi moved alongside Thornton and Pavelski while Couture centered Patrick Marleau and Joel Ward, while a quick third line of Karlsson, Tierney and Spaling displayed its offensive prowess. It just wasn't enough to get the job done.

"We've got to find a way to get the second one to tie the game up," Couture said. "We had chances, we had opportunities. We just didn't score. We had some nice looks we didn't capitalize on."

Martin said, "It's tight on both sides. We had some opportunities we didn't capitalize on. It's disappointing and a tough one for us."

Couture fired a shot off the shoulder of Murray with 5:01 left following a turnover by Pittsburgh defenseman Kris Letang. Marleau drew iron, and the San Jose power play failed for a second time late when it managed one shot by defenseman Brent Burns.

NOTES: Sharks LW Tomas Hertl (lower-body injury) missed his second straight contest in Game 4 on Monday. "Day-to-day. He's out tonight," San Jose coach Peter DeBoer said. Hertl sustained a lower-body injury believed to be to his left ankle in overtime of Game 2. A Czech report suggested Hertl is out for the series with a knee injury. ... Penguins rookie G Matt Murray bounced back from a playoff loss on May 20 to go 4-0 in Pittsburgh's next four games before losing Game 3 against the Sharks. ... San Jose's captain C Joe Pavelski has no goals and no points with four shots in the series. He produced a series-high five shots on goal Monday.