Boston — Yermín Mercedes opened Chicago's three-run fourth inning with a long homer, and the White Sox completed a sweep of their split-admission doubleheader against the Boston Red Sox on Sunday with a 5-1 victory.

Nick Madrigal had two hits and drove in two runs for Chicago, which climbed back to .500 at 8-8.

In the opener, Tim Anderson homered on the game's first pitch and Dallas Keuchel pitched five solid innings in a 3-2 victory.

The teams play the series finale Monday morning in Boston's annual Patriots' Day Game with a scheduled 11:05 a.m. first pitch at Fenway Park. Lucas Giolito (1-0, 2.55 ERA) is slated to go for the White Sox against Nathan Eovaldi (2-1, 2.08).

"It's a body check to get back mentally," White Sox manager Tony La Russa said of the early start.

For the first time since the Red Sox started playing their annual Patriots' Day game in 1959, Monday's contest will not be in held in conjunction with the Boston Marathon, which was moved to Oct. 11 due to the state's limits on crowds because of the pandemic.

J.D. Martinez had an RBI single for Boston's lone run in the second game.

Back wearing their traditional white uniforms with red letters and numbers in the nightcap, the Red Sox lost for the third time in four games after their nine-game winning streak.

Mercedes hit a changeup from Martín Pérez (0-1) off a backwall behind the batter's eye, a drive estimated at 431 feet. Danny Mendick had a bloop RBI single and Madrigal a run-scoring, hustle double to make it 4-0.

"I tried to throw a changeup down and away, but it stayed away in the zone," Pérez said. "He hit that pitch very good."

Mercedes enjoyed his first Fenway homer.

"It was really exciting. I've never hit a home run in Fenway," Mercedes said. "I've seen a lot of famous players play here."

Matt Foster (1-1) got five outs in scoreless relief for the win. Liam Hendriks got the final three outs in both games.

Chicago's bullpen went a combined six innings of scoreless relief in the two games.

"I'm telling you, we're going to have a really good bullpen," La Russa said.

The Red Sox were held to four hits in the nightcap.

"Stuff-wise, it's one of the toughest staffs in the big leagues," Boston manager Alex Cora said. "They've got velo and secondary pitches. They were good."

Pérez was tagged for four runs and seven hits in 3 [2/3] innings.

The Red Sox wore their yellow-and-blue City Series uniforms in the first game for the second straight day, honoring the Marathon with the colors that stretch across the finish line of the famous race.

Yasmani Grandal had an RBI double and Yoán Moncada drove in a run with a single for the White Sox. Keuchel (1-0) gave up two runs and Hendriks got his second save.

"Obviously, going in the first game, it was like 'How are you feeling?'" Hendriks said. "The first game I didn't feel great. It was a little bit of a grind. Game 2, I was able to have a little better location, a little better feel."

Anderson sent a 96.8 mph fastball from Tanner Houck (0-2) into Boston's bullpen.

Kiké Hernández homered around the right-field foul pole for Boston.

The doubleheader was scheduled after Friday's game was postponed due to snow and rain.

THROW OUT THE NUMBERS

Cora had a simple explanation, joking why left-hander Pérez was starting the second game.

"We dig into analytics and sabermetrics and all that, we found out that Martín is actually not a morning person, so we decided to go with Tanner," Cora said, smiling. "I can tell. We had a lot of day games. You didn't see him walking around the clubhouse a lot."

SHORT LEASH

Chicago starter Michael Kopech, a highly touted Red Sox prospect who was dealt to the White Sox in the Chris Sale trade in 2016, was pulled after he gave up his first hit in the fourth inning of the second game. He was charged with a run, struck out four and walked one.

TRAINER'S ROOM

White Sox: La Russa gave Anderson the second game off because "he was on the bases so much." Anderson said: "I want to play. I did my homework on the pitcher because I thought he was pitching the first game." ... After the game. La Russa said RHP Lance Lynn would miss his next scheduled start Wednesday because of something with "his neck, his shoulder" but he should miss only one.

Red Sox: Catcher Christian Vázquez was back in the lineup after two games off. ... Houck was hit on the lower body by Anderson's grounder for a single in the fifth. Houck said after that he felt fine.