The key second-half player for all 30 teams

Chris Sale needs to get turned around to help the defending champs earn another playoff appearance. Michael Dwyer/AP Photo

As the second half begins with most MLB teams still in the playoff hunt, there are multiple competitive races that could be decided by just a game or two. The difference between reaching October action and a season ending after game No. 162 might hinge on a key player or two performing better than expected, or getting back to a previously established level of performance after a tough first half.

What follows is one key player on each team to watch in the second half of the season who might change the course of a playoff race. For those teams not in contention, a key player worth watching is listed for clubs looking to reconfigure their rosters and rebuild for next year.

American League

Baltimore Orioles: Richie Martin

The Orioles shortstop was seen as a potential steal in the Rule 5 draft last winter, but Martin has not adjusted well to the jump from Double-A to the big leagues, with a .219 on-base percentage and very little power. He took a while to adjust at Double-A when he was promoted in 2017, and his second half might help determine whether he stays on the MLB roster next season and becomes a bigger part of Baltimore's rebuild.

Boston Red Sox: Chris Sale

Over his past four turns, Sale has struck out 30 batters and walked just six, but he's also averaging 5⅓ innings per start and has given up six homers and 19 runs. Last summer, Sale pitched just 29 second-half innings, but the Red Sox could afford to be cautious with their 2018 playoff spot secure. This season, every win could matter the rest of the way and they'll need Sale at his best to earn a shot at defending their World Series title.