SEATTLE -- For starters, the rotation was tremendous for the Red Sox.

Garrett Whitlock was the latest to step up, going five strong innings (three hits, one run, no walks, eight strikeouts) to help manager Alex Cora’s team salvage a season-opening, four-game split in Sunday’s 5-1 victory over the Mariners.

Given that the rotation was the biggest area of concern for Boston last season and the only external addition (Lucas Giolito) in the offseason won’t throw a pitch this season, it was reasonable for that group to be scrutinized.

In the Opening Series, the Red Sox not only quelled some fears, but joined some rare company in the process.

Over the four games in Seattle, Red Sox starters registered a 1.64 ERA. In the Wild Card era (which started in 1995), the only Boston team to do better in the first four games occurred in 2018 (0.75) and 1999 (1.09).

The 0.68 WHIP is the best opening four-game stretch since at least 1906.

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

All four starters reached Cora’s stated goal of five innings, In fact, Nick Pivetta and Kutter Crawford both went six. In 22 innings, the starters had one walk and 27 strikeouts at T-Mobile Park.

“They worked ahead in a lot of counts and did a really good job of getting us off the field and put together some really, really solid starts,” said pitching coach Andrew Bailey. “Now, we’re excited for tomorrow.”

Tanner Houck will complete the first cycle through the rotation when he opens a three-game series in Oakland on Monday night.

Perhaps the biggest modification the Red Sox made over the winter was with their pitching infrastructure. It started with the hiring of Craig Breslow as chief baseball officer, and continued with the additions of Bailey and director of pitching Justin Willard. The pitchers have bought in.

“It’s really big,” said Whitlock. “We build off of each other. We're all there competing with each other and cheering each other on so it was huge to rally together. We’ll be behind Tanner tomorrow to just keep it going.”

While Bailey is considered one of the best in the business at putting together a script for his pitchers, Whitlock and catcher Reese McGuire made a key adjustment in the middle innings on Sunday to keep the Mariners at bay.

“We made some adjustments today,” said Cora. “Halfway through the game, we changed the script. It seems like they were sitting on soft [pitches] and Whit was able to use his sinker. I think him and Reese did an outstanding job recognizing what was going on in front of them. And they took charge and took advantage of those certain counts.”

The Mariners, renowned for their rotation, had some pretty impressive starting pitching of their own in this series.

Thanks in large part to a big swing from Enmanuel Valdez for a three-run homer in the top of the fourth that snapped a 1-1 tie, the Red Sox were able to avoid losing their first series of the season.

“It was a huge momentum shift,” said Whitlock. “I mean, he lit us up in the dugout. That was awesome to watch.”

And after the big hit, the Red Sox didn’t allow a run the rest of the afternoon.

“I think these guys are really talented,” Bailey said. “We have a talented bunch and for them to go out there [and perform], they’re built up properly, and had a really good Spring Training and now we’ll try to keep the momentum going, I think that energy feeds off each other and that's a good situation to be in. I’m really proud of the group and we’ve got a lot of games left, so let’s stay the course.”

While Pivetta is the elder statesman of the group at 31, the other four starters are all between 24 and 27 years old.

“We've been talking about these guys for a while,” said Cora. “They're very talented. We’re going to miss Lucas, but at the same time, these guys are getting a chance to perform and the first four have been solid.”

For the first four games, they were a grade above solid.