"You know those turkey legs with those tendons going down the middle?" Wellemeyer said. "That's what it feels like."
The aggravation in his right arm runs down the top and the side of his forearm and into his wrist.
Wellemeyer was scratched from his start last week and returned to pitch against the Phillies on Friday night. The appearance did not go well, however, and he lasted only 3 1/3 innings and gave up eight earned runs.
He admitted the injury was on his mind following the Cardinals' 20-2 loss to the Phillies.
But regardless of any pain he is feeling, he believes he will be available to make his next start. Wellemeyer said the arm is feeling better and he will throw a side session Tuesday to determine if he can pitch in a game.
"I think I'll be able to make it, judging by how it feels right now," Wellemeyer said. "I think a couple of days' rest will help it out."
If Wellemeyer cannot go, one option to fill in for him is Anthony Reyes. Reyes was called up on Saturday for outfielder Joe Mather, who the Cardinals optioned to Triple-A Memphis.
Manager Tony La Russa, however, did not say Reyes will replace Wellemeyer, because it will depend if the Cardinals need Reyes to pitch out of the bullpen in the next three games.
Lee Hurwitz is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.