(CBS) The future is now for Ian Happ, a top Cubs prospect, but how long will it last?

With injuries piling up, the Cubs have called upon Happ, their 2015 first-round pick, to join the team Saturday in St. Louis. The team optioned reliever Felix Pena to Triple-A Iowa. Happ is the Cubs’ second-ranked prospect, according to MLB.com and Baseball America, trailing only outfielder Eloy Jimenez.

Happ will hit second in the batting order and play right field. He has primarily played second base and outfield during his minor league career.

The Cubs played without Kris Bryant in a 3-2 win over the Cardinals on Friday after he was a late scratch from the lineup with a stomach illness. His replacement, outfielder Jon Jay, left in the second inning with back spasms. Tommy La Stella then took over and hit a home run that proved to be the difference in the game.

Shortstop Addison Russell also remains sidelined with shoulder soreness, and second baseman Ben Zobrist is dealing with a back ailment. They’re all considered day-to-day. Outfielder Jason Heyward is expected to be activated from the 10-day disabled list prior to the homestand starting Tuesday at Wrigley Field.

Happ is hitting .298 with a .362 on-base percentage in Iowa this season. He had nine home runs and 25 RBIs in 26 games. It’s expected that he will be optioned back to Iowa when the Cubs have better health.

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