Rob Biertempfel tweets that Jordy Mercer is in Pittsburgh and will be activated if Alex Presley is placed on the disabled list.
Presley left Monday's game after diving for a ball in the first inning and suffering what appeared to be whiplash as his head never hit the turf.
Eric Fryer also remains on the roster and the team needs to make a decision on Chris Leroux, most likely tomorrow.
UPDATE: Rob now tweets that if Rod Barajas' knee is okay, Fryer will be sent down and Mercer will take his spot. Otherwise he will take Presley's spot if he is placed on the new 7-day concussion DL.
In other news, the Astros did indeed trade Carlos Lee, who was lifted late in today's game. He went to Miami for Matt Dominguez and Rob Rasmussen.