The Braves are optimistic that there is nothing seriously wrong, but Cormier may not be ready to start the season.
That would leave just five candidates for the five spots in the rotation, with Kyle Davies and Mark Redman following John Smoltz, Tim Hudson and Chuck James.
Cox isn't counting Cormier out yet, though.
"Hopefully," the manager said when asked if he thought the right-hander might be ready to start the season.
"He said he had it before in 2005, and it took only two or three days," Cox added.
The discomfort isn't in the labrum or rotator cuff area, but rather under the shoulder.
"Nothing popped," Cormier said. "I didn't feel anything like that. It's kind of stiff and sore. Hopefully it will go away."
Cormier, who came into the start against the Astros with a 3-0 record and 1.29 ERA in the Grapefruit League, retired the first five batters and would have been out of the second inning if shortstop Chris Woodward hadn't booted a grounder.
But Cormier felt something after the pitch and had to come out of the game.
"I just wanted to be very cautious about it and not do anything crazy and cause more damage," Cormier said.
Meanwhile, the Braves are glad they had an extra starter available.
"You want six guys ready every spring if you can," Cox said.
If Cormier is OK, he is scheduled to share time with Redman in the final exhibition game on Saturday against the White Sox in Atlanta.
Redman, the veteran left-hander, was officially purchased from Triple-A Richmond after being a non-roster invitee.
Redman had his first rough outing Monday, allowing four homers and six earned runs in six innings during a Minor League game. He was signed after Mike Hampton strained an oblique muscle early in camp. Hampton is expected to be ready to pitch as early as May.
Not a pretty sight: Matt Diaz looked more like a hockey player than a baseball player after a freak mishap during batting practice left him with a chipped right front tooth.
Diaz was reaching for a doughnut weight outside the batting cage when he was hit in the face by Chris Woodward's backswing.
"That's the hardest hit you've had all spring, Woody," Craig Wilson joked.
But it was no laughing matter as Diaz lay on the ground and teammates looked in the grass for the missing part of his tooth, finally finding it.
"Sorry, man," Woodward said.
Diaz returned to batting practice, but he was scratched from the lineup so that he could visit his hometown dentist in Lakeland to have a temporary crown put on.
Justice to be honored: David Justice, best remembered for his decisive homer in the 1995 World Series, will be this year's inductee to the Braves Hall of Fame.
Justice will be honored at the ninth annual Braves Hall of Fame luncheon on Aug. 17. The Braves will play the Diamondbacks that night and members of the 1957 World Series champion Milwaukee Braves will be recognized during the festivities.
Justice was the National League Rookie of the Year in 1990, and finished second in the league in homers (40) and RBIs (120) in 1993. But the outfielder is best remembered for his 1995 home run that beat the Indians, 1-0, in Game 6 and gave Atlanta its only World Series title.
Justice hit his blast in the sixth inning at Atlanta-Fulton County Stadium and Tom Glavine made the run stand up, allowing one hit in eight innings. Mark Wohlers pitched the ninth.
Justice was traded to the Indians during Spring Training in 1997 and completed his career with the Yankees and Athletics. He finished with 305 homers and a .279 average.
Prado keeps impressing: Martin Prado drove in three runs in the Braves' 6-4 victory over the Astros and also made two good plays at second base.
Prado, batting .366, had a two-run single and a sacrifice fly. Doug Clark, filling in for Diaz, raised his average to .464 with two hits and drove in a run.
Tyler Yates may have locked up the final spot in the bullpen with his best outing of the spring. The right-hander struck out two in a scoreless eighth inning, allowing one single.
Coming up: The Braves will play the Tigers on Tuesday night at Disney's Wide World of Sports, with Smoltz making his final spring start. First pitch is scheduled for 7:05 p.m. ET.