Boston Red Sox outfielder Wilyer Abreu was supposed to have the first game of Sunday’s doubleheader against the St. Louis Cardinals off. Instead, he pinch-hit and delivered a walk-off hit.

So, how did Abreu follow that up in Game 2? All the 25-year-old slugger did was turn heads with another outstanding performance.

Abreu stayed red-hot at the plate, going 2-for-6 with three RBIs from the cleanup spot in the order as the Red Sox thumped the Cardinals, 18-7, at Fenway Park to earn the series sweep.

The strong showing earned Abreu, who dealt with a viral gastrointestinal illness at the start of spring training, a piece of franchise history, too. According to Red Sox senior manager of media relations and baseball information J.P. Long, Abreu’s .483 batting average and .595 on-base percentage are the highest of any Red Sox player in history through the first 10 games with a minimum of 25 plate appearances.

“I felt confident when I left spring training that I was healthy and ready to have a very good season,” Abreu told reporters following his walk-off hit through translator Carlos Villoria Benítez, per MassLive’s Christopher Smith. “Obviously this is way better than I expected.”

By the end of Sunday’s rout, Abreu heard MVP chants when he came to the plate from the Fenway faithful, and for good reason, too. He got Boston’s offense rolling in the bottom of the first with a ringing single to right. In his next at-bat the following inning, he laced a double into the left-center gap, giving the Red Sox a 6-1 lead.

“Try to use the whole field,” said Abreu, who also took his walk-off hit to the opposite field. “It’s a huge help — even more here at Fenway when we try to use the Monster to our advantage. If I’m able to do that consistently, it’s going to be a very good year for me.”

But Abreu just didn’t do it with the bat. He also cut down Lars Nootbaar trying to go from first to third on a single from Willson Contreras in the top of the third. Abreu unleashed a picture-perfect throw to get Nootbaar as Alex Bregman didn’t even have to move his glove to apply the tag.

“He worked hard in the offseason with his swing, his body,” Red Sox manager Alex Cora told reporters, per NESN. “Right now, his start is amazing.”

Here are more notes from Sunday’s Red Sox-Cardinals doubleheader:

— Any concerns about the Red Sox offense quickly went away following the series against the Cardinals. They scored 36 runs and collected 46 hits in the three games. Boston erupted offensively in the nightcap of the doubleheader with 22 hits, including nine doubles.”

— Much was made of Bregman’s success at Fenway Park in his career when he signed a three-year, $120 million deal with the Red Sox. And the veteran third baseman showed in his first series at the venerable ballpark in the home uniform that it’s no fluke, either. Bregman went 6-for-13 with three doubles and two walks in three games against the Cardinals and had a monster performance in the second game of the twin bill. Bregman went 4-for-6 with a three-run home run — a 411-foot blast to center field — and six RBIs.

— Rafael Devers’ major slump appears to be a thing of the past. Devers hit his first home run of the season in Game 1 and followed that up by going 4-for-4 with three RBIs in Game 2. Devers consistently drove the ball to left-center, a good sign that he’s in a much better place at the plate. The left-handed slugger now has 10 hits in his last 19 at-bats.

“The at-bats are really good. They’ve been really good throughout, just swinging and missing,” Cora said. “He’s not chasing. He’s staying in the zone. Little bit little, the swing is back to normal. That was impressive.”

— Hunter Dobbins made his MLB debut in the nightcap as the Red Sox gave the start on the mound to the 25-year-old right-hander, who was the 27th man on the roster for the doubleheader. Dobbins showcased his impressive arsenal, which included his fastball topping out at 97 mph, across five innings to earn the win. He scattered eight hits while surrendering two runs and two walks to go along with five strikeouts. Dobbins is ranked as the No. 13 prospect for the Red Sox by MLB Pipeline.

— Sean Newcomb made his first start at Fenway Park as a member of the Red Sox and the outing had more meaning to the left-hander since he grew up in Middleboro, Mass. Newcomb allowed runners on base every inning, but continuously worked out of jams. He gave up just one run on six hits with three walks while striking out five in 4 2/3 innings.

“It was special,” Newcomb told reporters, per NESN. “Just looking to kind of stay within myself. It was definitely cool, taking a couple of extra minutes before I warmed up to just soak it all in.”

— The Red Sox open up a three-game series from Fenway Park on Monday against the Toronto Blue Jays. Richard Fitts will oppose Easton Lucas. First pitch is scheduled for 6:45 p.m. ET and you can catch complete coverage on NESN.