The Rockies' reeling rotation has taken another major hit. Right-hander Tyler Chatwood will miss the rest of the season and is scheduled to undergo Tommy John elbow surgery, a major-league source confirmed Thursday. Chatwood will likely undergo surgery sometime next week. That means he will likely miss most, if not all, of the 2015 season. Chatwood, counted on to be a consistent part of the starting pitching corps this season, has not pitched since April 29 when he left a game because of tightness in his elbow. The original diagnosis was a right flexor strain and inflammation in his elbow. Chatwood was making slow progress as he attempted to work his way back, but he left a live batting practice session last week, clearly upset with how is elbow was responded when he attempted to throwing breaking balls. Chatwood, 24, already was on the 60-day disabled list because of the elbow injury. He made four starts this season, going 1-0 with a 4.34 ERA. He also missed his first two starts to begin the season after suffering a left hamstring injury when he stretched a double into a triple during a Cactus League game near the end of spring training.