The Vegas Golden Knights needed their goaltender to help them survive the first period Sunday.

By the time they left Buffalo, they had plenty more to feel good about.

Tomas Hertl scored twice in the third period, Mitch Marner had a shorthanded goal and an assist, and Adin Hill stopped 28 of 29 shots as Vegas defeated the Sabres 4-1 at KeyBank Center.

Jack Eichel also scored against his former team, and Ivan Barbashev collected two assists for the Golden Knights (12-5-2), who finished their four-game Eastern trip 3-0-1.

“Some tight games and some timely goals and some huge saves,” Eichel said. “A lot of credit to the guys here after a long road trip finding a way to win here in the afternoon.”

Vegas outscored its opponents 11-6 during the trip, winning three straight after opening with a shootout loss in Boston.

Coach Ryan Craig pointed to a clear change after the opening period.

“Our ability to check, our ability to win pucks back, our level raised,” Craig said. “And it was the difference in the game.”

Buffalo outshot Vegas 14-6 in the first period, but Hill kept the game scoreless before the Golden Knights found their footing.

“We didn’t obviously have our best period,” Hill said. “But we found a way to keep it at 0-0 at the end of the period. Our guys blocked a lot of big shots.”

Marner and Eichel scored in the second period before Hertl put the Sabers away in the third. Beck Malenstyn scored Buffalo’s only goal as the Sabres fell to 8-6-3.

The Golden Knights turned a Buffalo power play into the beginning of their breakthrough.

Marner scored an unassisted shorthanded goal at 12:17 of the second period, and Eichel followed just 86 seconds later to give Vegas a 2-0 advantage.

“I think sometimes the kill can get you going,” Marner said. “I think it kind of gets you on your toes more, gets you anticipating plays.”

Marner’s goal was Vegas’ fourth shorthanded tally of the season, tying the Golden Knights for the NHL lead.

His edge work helped produce the finish, though his later explanation suggested instinct played a significant role.

“I didn’t really know what I was doing until I did it,” Marner said. “So I think that obviously keeps people guessing as well.”

Eichel then scored his eighth goal of the season off an assist from Barbashev at 13:43.

The sequence rewarded a team that had stayed within reach during Buffalo’s stronger opening period. It also reflected the patience Marner believes has accompanied Vegas’ recent defensive improvement.

“The great thing is we’re not getting frustrated with not scoring goals,” Marner said. “We’re defending very, very well right now.”

Vegas killed 14 of 15 penalties during the four-game trip, a 93.3 percent success rate that helped protect narrow margins throughout the week.

The Golden Knights collected a point in Boston before winning one-goal games in Pittsburgh and Detroit. Their ability to keep opponents from converting with the extra skater repeatedly gave them an opportunity to secure points.

Craig traced the importance of those kills from the five-minute major in Boston through Sunday’s breakthrough.

“The Boston one keeps us in,” Craig said. “The Pittsburgh one late allows us for a chance to win the game. This one keeps us right at zeros, right, before Mitch scores. So very timely.”

For Eichel, the results represented a payoff for work that had been better than the early numbers suggested.

“I thought our penalty kill had been good even earlier in the year,” he said. “They were just finding ways to score, and I thought we’ve done a good job keeping the puck out of our net.”

That improvement fit the broader defensive picture. Vegas allowed two goals apiece in Boston and Pittsburgh, then one each in Detroit and Buffalo.

Hill and Carter Hart gave the Golden Knights a chance every night, while the penalty killers helped keep difficult stretches from becoming decisive ones.

“There’s a commitment to our team that is there,” Craig said.

Hertl made sure Buffalo’s third-period breakthrough did not become the start of a comeback.

Malenstyn cut Vegas’ lead to 2-1 at 4:26, giving the Sabres more than 15 minutes to chase an equalizer.

Hertl answered 77 seconds later.

His goal at 5:43, assisted by Marner, restored the two-goal advantage and relieved the pressure on Hill after Buffalo had finally beaten him.

“They got that one goal there to make it a 2-1 game,” Hill said. “And then it was maybe two shifts later, Hertz finds a way to bury one.”

Hertl added his second goal at 10:00, with Barbashev and Shea Theodore recording the assists, to put Vegas ahead 4-1.

“Two beautiful goals by Tommy,” Eichel said. “Gave us a little bit of comfort. And I thought we played well with the lead.”

The goals were Hertl’s eighth and ninth of the season. He also scored twice in Tuesday’s victory at Pittsburgh, giving him four goals over the final three games of the trip.

Both Pittsburgh goals came on the power play. Both Buffalo goals came at even strength.

Craig credited the defensive work that preceded Sunday’s finishes, including Marner’s checking and the backchecking before the transition on the second goal.

“Those goals in the third are a result of us checking,” Craig said.

The Golden Knights return to T-Mobile Arena to face the Utah Mammoth on Wednesday at 6:30 p.m. Pacific.

The game opens a five-game homestand that also includes Nashville, Vancouver and consecutive matchups against Dallas.

Vegas returns with 26 points through 19 games, although Eichel resisted declaring the successful trip a defining stretch of the season.

“I don’t know if you want to define your season on a trip in the early part of November,” he said. “But I think there’s a lot of things we can take from our game and what made us successful and what we did well.”

Vegas Golden Knights center Tomas Hertl (48) scores a goal on Buffalo Sabres goaltender Colten Ellis (92) during the third period at KeyBank Center.