The Cubs hope to win the series with Travis Wood (5-11), who has one win since the All-Star break, getting the start against the Astros' Fernando Abad (0-3).
The Cubs have 20 games left to avoid the 100-loss mark and need to go 8-12 to do so. Wood had lost eight in a row until his win last Friday against the Pittsburgh Pirates, and he's 1-1 with a 1.35 ERA against the Astros this season.
Cubs outfielder Brett Jackson is dealing with a bruised right knee but cold be available off the bench Wednesday. Anthony Rizzo isn't expected to play after injuring his shoulder in a collision at first base during Tuesday's game.
Wednesday's game starts at 7:05 p.m. CT. and is on the air on CSN+ and WGN 720 radio.
For more coverage of this series, stay tuned to SB Nation Chicago. For more in-depth coverage, check out Cubs blog Bleed Cubbie Blue and Astros blog Crawfish Boxes. And for more news, notes and analysis from around the league, head over to Baseball Nation.