There was plenty of uncertainty surrounding the Boston Red Sox starting rotation entering this season.

But even though it has been four games, those concerns have at least lessened a little bit.

Garrett Whitlock kept the string of terrific starting pitching going for the Red Sox on Sunday in their 5-1 win over the Seattle Mariners at T-Mobile Park. Whitlock tossed five innings of one-run ball and surrendered just three hits while striking out eight and walking none.

Boston really couldn’t have envisioned better production from its starting staff to begin the season. Brayan Bello, Nick Pivetta, Kutter Crawford and Whitlock combined to allow four earned runs and one walk while registering 27 strikeouts in 22 innings.

“I know we’re going to miss Lucas (Giolito), but at the same time, they got a chance to perform,” Red Sox manager Alex Cora told reporters, as seen on NESN postgame coverage. “The first four have been solid.”

The questions coming at the Red Sox starters were justified. Despite his high upside, Bello still is unproven as an ace of a staff. Pivetta can be streaky on the mound while Crawford, Whitlock and Tanner Houck are trying to prove they’re better in a starting role than in the bullpen.

Red Sox fans clamored for the team to add a pitcher like Jordan Montgomery to the rotation. They didn’t and that could pay off if — a big if by the way — the Red Sox starters keep this up.

“Like I’ve been saying all along, I’ve been believing we’re going to pitch,” Cora said.

The Red Sox starters certainly have done their part and were the main reason why Boston earned a split in their first series of the season.

Now, it will be on Houck to keep things up before going back through the rotation again to see if they can produce similar results.

“We build off each other,” Whitlock told reporters, as seen on NESN postgame coverage. “We’re all there competing with each other and cheering each other on. It was huge to kind of just (come) together. And same thing, we’ll be behind Tanner (Monday) and just keep it going.”

Justin Slaten will always remember his MLB debut for allowing a walk-off single to Julio Rodríguez on Saturday night. But Slaten created a much better memory Sunday. The right-handed reliever tossed 2 1/3 scoreless innings and threw 12 of his 15 pitches for strikes to record his first career save. He punctuated his outing in style by striking out Dylan Moore.

“As good as last night was being the major league debut, it’s awesome, but still you kind of have a little bit of a sour taste in your mouth,” Slaten told reporters, as seen on NESN postgame coverage. “So, to get the opportunity to come right back at it today, it was everything. Just to feel like I had that support behind me just to go and give it another try, it was great.”

— Star third baseman Rafael Devers sat out the last two games due to lingering left shoulder soreness. He made his return Sunday and went 1-for-5 with a walk.

— Enmanuel Valdez is trying to make the most of his opportunity at second base with Vaughn Grissom on the injured list. Valdez went 1-for-4 in the win, but his hit was critical. He broke a 1-1 deadlock in the top of the fourth with a three-run home run.

“He was long in the second pitch and then he got short in the last one, and that’s what we’re looking for,” Cora said. “You got to stay humble and sometimes when you’re humbled, big things happen. The kid, he can hit. That’s the reason he’s playing.”

— Kenley Jansen didn’t pitch in Saturday’s extra-inning loss due to back tightness. It looked like he was available to pitch Sunday. He warmed up in the bullpen as Slaten closed things out, per multiple reports.

— The only real blemish the Red Sox had in their series finale with the Mariners came on the base paths. Wilyer Abreu was picked off second and Trevor Story was caught trying to steal second.

— Boston’s 10-game road trip to begin the season rolls on to the next city as the Red Sox open a three-game series with the Oakland Athletics starting on Monday. First pitch from the Oakland Coliseum is scheduled for 9:40 p.m. ET, and you can watch the game, plus an hour of pregame coverage.