Manager Craig Counsell revealed Saturday that Happ has a mild left hamstring strain, Meghan Montemurro of the Chicago Tribune reports.
Counsell is optimistic that Happ will be ready for Opening Day, but the outfielder has no timeline to return to spring training games. Happ slashed .248/.360/.431 with 21 home runs and a career-high 84 RBI over 691 plate appearances in 2023.