Two of the bigger pieces to the Cubs' pitching puzzle are going on the disabled list.
John Lackey and Hector Rondon were placed on the 15-day disabled list, with minor leaguers Rob Zastryzny and Felix Pena added to the active roster in their place, the Cubs announced Friday.
Lackey was originally announced to just receive an additional few days of rest, with Mike Montgomery taking his place in the rotation during this weekend's series against the Colorado Rockies. But the right-handed starter now went to the DL after exiting his last start this past Sunday with a shoulder injury.
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Rondon was out of action for a week and a half while dealing with triceps soreness. He returned in an ugly performance in that same game this past Sunday, giving up four runs on four hits including a pair of home runs while recording just one out in the eighth inning of a 6-4 loss to the St. Louis Cardinals. He also pitched a scoreless inning in the first game of Tuesday's doubleheader sweep of the Milwaukee Brewers.
Zastryzny's first appearance with the Cubs will be his major league debut. In four seasons in the minors, the lefty has a 4.60 ERA in 334 1/3 innings pitched. This season between Double-A Tennessee and Triple-A Iowa, he is 10-5 in 23 starts with a 4.31 ERA, striking out 119 batters in 135 2/3 innings.
Pena has also never made a major league appearance. In 36 appaearances this season at Triple-A Iowa, the right-handed reliever has a 3.41 ERA in 63 1/3 innings of work.