The Colorado Rockies, who sit fourth in the National League West, may lose one of their top players for a significant portion of the 2012 season, as shortstop Troy Tulowitzki is set to undergo surgery on his groin Thursday. There is no timetable for his return.

Tulowitzki originally injured his groin in a game against the Dodgers in late May while breaking out of the batter’s box. He re-aggravated the injury while playing in a rehab game June 13th and returned to Denver for further testing.

This season, he has a .287/.360/.486 slash line with eight home runs. Marco Scutaro will likely continue to play shortstop for the Rockies in his absence.