Gonzalez (shoulder) threw off flat ground Sunday in preparation for his first bullpen session Thursday, Daryl Van Schouwen of the Chicago Sun-Times reports.

EDGE Analysis

Gonzalez spun a few curveballs and let go of some changeups during the session. ''All in all, it's big-time progress to where I started to where I am now,'' said Gonzalez, 34, who has been working to get his slightly sore left shoulder ready for the season. ''There's nothing going to keep me from being ready for Opening Day. I've just got to keep working hard.'' Gonzalez figures to slot in at the back end of the rotation once he's ready to go.