Cubs right fielder Jason Heyward was scratched just before game time Tuesday because of a right hamstring "cramping," the club said.
Heyward, who missed more than two weeks during the first half of the season because of a left hamstring strain, was replaced in the lineup by rookie Alfonso Rivas.
Heyward has struggled most of the season but was 3-for-8 the last two games with a homer Sunday and a triple Monday as the Cubs extended their season-long winning streak to seven games.
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Rivas, who debuted just over a week ago, made his second start in the outfield, in left (with Patrick Wisdom shifting from left to right to cover Heyward).