Tulowitzki is reportedly feeling soreness in his side similar to what one would feel with an oblique injury. If he strained his oblique, Tulowitzki will likely need a stint on the disabled list and would miss at least two weeks. It does not sound like a DL stint is in the cards yet, but the Rockies will monitor him closely as he sits out for likely a few days.
Tulowitzki missed a month earlier this season when soreness in his side turned out to be a broken rib. He also played in just 47 games in 2012 after having surgery on his left groin.
Jonathan Herrera will start at shortstop in Tulowitzki's place. Herrera has been used as a utility player by the Rockies this season, but is a natural shortstop and will likely continue to play the position until Tulowitzki can return.