Cook, out with a right shoulder injury since Aug. 22, threw off the mound on Friday as well, and the next step in his recovery process will be to test the shoulder in a simulated game on Tuesday.
Manager Jim Tracy only caught a glimpse of Cook's throwing session from afar, but liked what he saw nonetheless. Moreso, Tracy interpreted the presence of both Cook and Contreras as an indication that both are progressing well.
"We've got a full bullpen session [Sunday]," Tracy said. "It's a good sign. I happened to look over my shoulder and it looked to me like the ball was coming out of Aaron Cook's hand pretty well. That's basically where we're at on the pitching front."
Pitching coach Bob Apodaca had a closer look, and was equally encouraged. Regarding Contreras, who exited last week with a right quadriceps strain, Apodaca said the only limitation is fielding rather than anything related to pitching.
"Contreras was fabulous," Apodaca said. "Contreras is still having trouble as far as moving laterally and fielding his position. As far as his work off the mound, he was fine. Unfortunately, there's no designated fielder for pitchers. He has still got to run around."
Cook also showed positive signs as he tuned up for the simulated game, one of the likely two he will throw before heading to Arizona to pitch in the Instructional League in advance of rejoining the big league club.
The sessions for both starters represent the general good fortune the Colorado pitching staff has experienced throughout the course of the season. Only three times, including Saturday's spot start by rookie Esmil Rogers, have the Rockies had to call upon a fill-in in the starting rotation.
"Knock on wood, we've been very, very fortunate as far as injuries -- key injuries," Apodaca said. "I think where teams really get caught is if you lose people in the starting rotation, and then you're going to have to go to either a spot starter or somebody from the Minor Leagues. But we've been very fortunate as far as health. I think that bodes well for any team that's going to contend."
With a postseason berth on the line, the club is clearly heartened by the signs of pitching reinforcements to come.
Tim Powers is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.