Reliever Mark Leiter Jr. comes up big in Cubs’ victory against Red Sox

Mark Leiter Jr. had no time to get comfortable in his bullpen chair Saturday.

Leiter was summoned after Cubs starter Alec Mills departed after only two batters because of tightness in his lower back, but he pitched with ease, limiting the Red Sox to three hits in 5⅓ innings as the Cubs earned a 3-1 victory that extended their winning streak to four games.

‘‘Big-time performance,’’ manager David Ross said after Leiter preserved most of the bullpen.

Leiter, who has shuttled between Triple-A Iowa and the Cubs this season, stranded Rafael Devers at second in the first and retired 13 of the first 15 batters he faced. He departed with two outs in the sixth after the Red Sox scored their lone run when Devers grounded into a double play.

‘‘For him to give us that length was impressive,’’ Ross said.

Leiter admitted it was ‘‘kind of a tough spot because [Mills’ injury] happened so fast,’’ but he praised the umpires for not rushing him while he was warming up.

Leiter, who was recalled from Iowa on June 21, hadn’t allowed a run in seven innings covering three appearances before Saturday. His previous seasonlong outing was four innings twice.

Leiter became the first Cubs reliever to earn a victory while pitching at least 5⅓ innings and allowing one run or fewer since Glendon Rusch on July 15, 2004.

Mills felt discomfort while striking out leadoff man Jarren Duran, then knew he had to leave after his back tightened while backing up third on Devers’ double.

‘‘It feels like a collection of the season came down to today,’’ said Mills, who has pitched only 17 2/3 innings because of back and quadriceps injuries.

Seiya in Milwaukee?

The long-awaited return of outfielder Seiya Suzuki might happen as soon as Monday against the Brewers in Milwaukee.

Ross acknowledged Suzuki is close to rejoining the Cubs, but how close is he?

‘‘Monday,’’ Ross said. ‘‘Maybe.’’

Suzuki went on the 10-day injured list May 27 with a sprained left ring finger, and his recovery has moved slowly. He went 1-for-3 with an RBI double for Iowa on Saturday and is 4-for-9 with two doubles, a home run and three RBI in his rehab assignment.

Suzuki’s return also would strengthen the Cubs’ defense in right field.

• Second baseman Nick Madrigal (strained left groin) increased his baserunning work and might start a rehab assignment by the middle of the week.

Hot plate dining

Ross and TV play-by-play man Jon Sciambi spent Friday night with a couple who submitted the highest bid to dine with them behind home plate at Wrigley Field.

The proceeds went to funding awareness for ALS, a charity Sciambi is involved with. Former White Sox pitcher Jon Garland visited the foursome, Ross said.

‘‘We had perfect weather and talked a lot of baseball,’’ Ross said. ‘‘A nice couple donated to that. It was nice to be able to help a good cause.’’