"Hopefully that will get me over the hump," Webb said.
Webb had surgery on his shoulder in August and was back on the mound throwing bullpen sessions in January. However he hit a plateau of sorts after the start of Spring Training and has not thrown off a mound since early March.
"It never hurt," Webb said. "It doesn't feel great, but it doesn't hurt bad. I still feel like I can't let it go. I still feel like I'm not ready to get on the mound yet. I can't take it to the mound."
How to get Webb over the hump has been the mystery of the spring.
"There are mental hurdles to clear," D-backs manager A.J. Hinch. "I think there are physical hurdles to clear in terms of the workload, and these dead periods show up from time to time in the recovery process. When to push him, when to lay back on him, when to accelerate his deals has been very hot and cold this spring. That's the frustrating part for everybody involved. It's been a little on again, off again."
Webb will be off for at least the next several days following the cortisone injection. Webb said that they opted for an injection rather than oral medication because it could better target the inflammation in the shoulder.
"Again, I don't know what's next," Hinch said. "It's important to get him healthy, and we feel like based on the doctor's report that this might be exactly what he needed. It's been a little slower for him than anybody anticipated, but it is what it is and now we have to try and get him better."
Initially, Webb hoped to be ready for the start of the season. Then he targeted late-April, which now is almost certainly out of reach.
The slowness of the recovery is hard to explain. By comparison, Major League pitchers Jeff Francis and Erik Bedard have been able to get on the mound quicker. Francis pitched in some instructional league games last fall after having the surgery seven months prior, while Bedard was pitching in the big leagues just under seven months after his procedure in 2008.
"Everybody heals differently," Webb said. "Healing is different from person to person."
When Webb is ready to throw again, he will play catch until he is able to get back up on the mound.
"I think until he can accelerate his arm at a speed that would represent a full-speed delivery, there's just no reason to do it," Hinch said of putting Webb on the mound. "Right now, arm strength and arm speed are the two things we're focused on."
Webb started on Opening Day last season and went just four innings against the Rockies. It was the only game action he saw all season.
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.