One team official recently referred to Lux as a player “still in our holster.” Another said the Dodgers could find at-bats for the versatile Chris Taylor and Kiké Hernández, both of whom recently came off the injured list, even if Lux entered the mix. 
The Dodgers have a history of giving top prospects a September apprenticeship. Corey Seager came up in September 2015 before taking over as the starting shortstop in 2016. Walker Buehler made his MLB debut as a reliever in September 2017, then joined the rotation in 2018. Catcher Will Smith wasn’t added to the active roster last September, but was with the team and sat in on meetings.
Lux is a left-handed hitter who could draw a fair number of starts in September against right-handed pitchers. The platoon-happy Dodgers could employ these two defensive alignments in the final four weeks of the season:

The 21-year-old Lux is a natural shortstop who has played some second base throughout this minor league career. Hernandez (58 starts) and Max Muncy (57 starts) have more or less platooned at second base this season, with Taylor (13 starts) seeing time there as well. Taylor and Hernandez are versatile enough to play the outfield, and Muncy could slide back over to first base.

Lux broke out offensively after getting stronger and using his legs more while adding more launch angle to his left-handed stroke. Those changes as well as his bat speed give him more power than most middle infielders. He’s an advanced hitter who has controlled the strike zone well and made consistent contact throughout his pro career, even when he wasn’t putting up big numbers.
Truth be told, few September call-ups have an impact. Most are extra bodies to soak up innings in blowouts and give regulars a break down the stretch. Sometimes non-contenders will use September to let a prospect get his feet wet before joining the team on a full-time basis next season. Rarely are September call-ups difference-makers in a postseason race though.
With his plus speed and savvy, Lux can steal bases and has the upside of a 25-25 player. He has the raw tools to play shortstop, including quickness, soft hands and solid arm strength, and he has gotten smoother at the position since turning pro. Lux, 21, is having a monster minor league season. He owns a .351/.425/.615 batting line with 25 homers in 108 games split between Double-A and Triple-A. In 44 Triple-A games, Lux is hitting .407/.493/.747 with 12 homers. ranks him the 10th-best prospect in baseball. Here’s a snippet of their scouting report:
In six days MLB teams can expand their active rosters from 25 players up to 40 players. September call-ups rules are set to change next year — teams will only be allowed to carry 28 players in September — but, this year, they remain the same. Teams can carry up to 40 players in the season’s final month.

Among the top prospects who could be summoned to the big leagues for the first time this September is Dodgers shortstop Gavin Lux, the team’s first round pick in 2016. Ken Rosenthal of The Athletic reports Los Angeles is considering calling up Lux.
Lux is not on the 40-man roster, so calling him up in September would requiring dropping someone else. That’s something the Dodgers will have to consider. Lux costs you another player. That said, letting a young player get his feet wet down the stretch can help prepare him to help you next year, like it did with Seager, Buehler, and Smith. It’s worth the roster move.

That still leaves Jedd Gyorko on the bench, plus the Dodgers have David Freese (hamstring), Alex Verdugo (oblique), and Tyler White (trap) on the injured list. They’re expected to return at various points in September. Point is, Los Angeles has a very deep roster yet enough versatility to ensure Lux gets plenty of playing time in September.
The Dodgers have baseball’s best record at 86-46 and they are 20 games up in the NL West. They don’t need Lux to help them pin down a division title or postseason spot. His September call-up would be a relatively low-pressure “show us what you can do, kid” opportunity that sets the stage for him to take over at second base in 2020.