As well as the Red Sox have played of late, Sunday served as a stark reminder of just how quickly things can change.

The Red Sox dropped the second game of a doubleheader by a 5-1 final at Fenway Park, suffering a sweep at the hands of the White Sox. Any momentum from Saturday’s win disappeared courtesy of shaky pitching, troublesome defense and a lack of timely hitting, giving Boston its first losing streak since the season-opening three-game sweep by the Orioles.

• Box score

Michael Kopech and a quartet of relievers held the Red Sox to one run on just four hits in the second game, while Dallas Keuchel led the White Sox to a 3-2 win in the opener with five innings of two-run ball. Boston hitters drew just one walk over 14 innings, resulting in only nine chances with a runner in scoring position all day.

“Stuff-wise, it’s one of the toughest staffs in the big leagues,” manager Alex Cora said. “They’ve got velo, they’ve got good secondary pitches. They were good the whole day.”

The teams will meet Monday in the annual 11:10 a.m. ET Patriots’ Day matinee as the Red Sox will try to earn a split of the four-game set.

“You turn the page,” Cora said. “Just like we did in Minnesota -- when you win two, you turn the page and you’ve got to be ready for tomorrow. … We're going to be OK. We’ve got a chance to split the series tomorrow, so that's the way we see it.”

Neither Boston starting pitcher was particularly sharp on Sunday. Martín Pérez scuffled through 3 2/3 innings, allowing four runs on seven hits, including a towering solo home run by Yermín Mercedes. Tanner Houck gave up three runs on six hits in 4 1/3 innings in the opener, but it was a lack of offense that doomed the Red Sox to their 0-2 day as the lineup stranded seven runners, struggling to come through in the clutch.

• Houck shows progress in loss

“I do believe in the first game we hit a few balls hard that changed the game, but in the second game, it was hard,” Cora said. “We had a chance there, and they brought in [Matt] Foster and he did a good job.”

Cora was talking about the fourth inning, when the Red Sox came to bat facing a 4-0 deficit after the White Sox scored three times in the top of the frame.

Kopech, the Red Sox’s first-round pick in the 2014 Draft who was dealt to the White Sox in the December 2016 Chris Sale trade, had retired the first nine batters he faced. (Yoán Moncada, the other major piece of the Sale trade, also hurt the Red Sox on Sunday with superb fielding at third base and the game-winning RBI in the first contest.)

Kopech’s perfect evening disappeared in the fourth with a leadoff walk of Kiké Hernández, then Alex Verdugo singled, ending the 24-year-old’s night. Foster came in and gave up an RBI single by J.D. Martinez, but the reliever limited the damage, retiring Xander Bogaerts, Rafael Devers and Marwin Gonzalez without allowing another run.

“We're going to run into [pitching] like this,” Cora said. “It happens.”

Nathan Eovaldi will try to salvage the split on Monday as the Red Sox look to curb their losing streak at two. Despite Sunday’s setback, Boston remains confident in itself, especially after rattling off a recent nine-game winning streak.

“We're good enough to compete with any team; we just need to stay together and stay focused,” Pérez said. “Everybody knows what they have to do to put everything together and win games.”