Justin Steele left Wednesday's game for an unknown reason after David Ross and the training staff checked on him in the third inning.
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Hayden Wesneski, another Cubs' starter, replaced Steele in the fourth inning.
Steele had a perfect game going through three innings before departing the game. His final stat line finished with 3.0 innings pitched, zero hits, zero runs, zero walks and one strikeout. He pitched 29 pitches, 19 of which were strikes.
The 27-year-old pitcher is having the best season of his career. He's holding a 2.77 ERA and 1.108 WHIP in 11 starts and 65 innings pitched. He's tallied 57 strikeouts and 16 walks so far this year.
Check back here for updates on Steele's status.