Gavin Lux will make his Dodgers debut Monday

Rosters expanded across baseball Sunday as the calendar flipped to September and the Dodgers added three veterans to their roster off the injured list for their 4-3 win over the Arizona Diamondbacks. They’ll add another at Dodger Stadium on Monday to more hype.

Gavin Lux, the organization’s top prospect, will join the Dodgers and make his major league debut against the Colorado Rockies. Dodgers manager Dave Roberts said Lux will start at second base.

“Gavin’s earned this opportunity,” Roberts said. “I think that’s kind of plain and simple.”

Lux, 21, stormed his way through the minor leagues over the last two years. A first-round pick in 2016, the middle infielder solidified himself as a bona fide prospect last season when he batted .324 with 15 home runs and a .913 on-base-plus-slugging percentage in 116 games between Class-A Rancho Cucamonga and double-A Tulsa.

He produced at a higher clip this year, batting .313 with 13 home runs and an .896 OPS in 64 games for Tulsa before getting called up to triple-A Oklahoma City. In 49 games for Oklahoma City, he hit .392 with 13 home runs and a 1.197 OPS. Between the two levels, he slashed .347/.421/.607 and accumulated 61 walks in 523 plate appearances.

Defensively, the Wisconsin native had throwing accuracy problems resurface in spring training that continued into the early part of the season. He corrected them and made 13 errors in 776 innings on defense, primarily at shortstop.

Over the last month, in preparation for a possible call-up to the majors, the Dodgers had Lux play second base. He made 12 starts there for Oklahoma City after six with Tulsa.

Sign up for our free Dodgers Dugout newsletter >>

Roberts said Lux will play regularly. Max Muncy’s wrist fracture, suffered last week, opens more opportunities at second base than initially thought. He can also spell Corey Seager at shortstop.

“I think we’re all excited to see him,” Roberts said. “It’s very exciting to see a young player who can play both sides of the baseball. Dynamic, organizational guy. To see his debut at home, we’re all excited.”

Players must be on the team’s 40-man roster by the end of Aug. 31 to be eligible for the postseason but there’s a loophole. If that player was in the organization by Aug. 31 and would replace someone on the injured list who has served the minimum amount of time for reinstatement, the club can petition the league to give that player playoff eligibility.

Reinforcements arrive

With rosters expanding Sunday, the Dodgers activated first baseman David Freese and right-handers Ross Stripling and Dylan Floro from the injured list.

The club is expected to recall players from Oklahoma City this week beyond Lux. Catcher Austin Barnes will be one of them. Other call-up possibilities include infielder Edwin Rios, outfielder Kyle Garlick, and right-handers JT Chargois and Josh Sborz.

Scott Alexander and Tyler White are out

Roberts ruled out the returns of left-hander Scott Alexander and first baseman Tyler White. Alexander, 30, hasn’t pitched since going on the injured list June 11 with forearm inflammation. He’ll finish the season with a 3.63 earned-run average in 28 appearances.

The Dodgers acquired White from the Houston Astros in July. He appeared in 12 games with Los Angeles, going one for 22. He was placed on the injured list with a right trapezoid strain Aug. 13.