PHOENIX — Arizona ace Brandon Webb is headed to the 15-day disabled list with tightness in his pitching shoulder.

The Diamondbacks decided to make the move, retroactive to Tuesday, after Webb tested his shoulder by playing catch on Sunday morning.

‘‘I feel like we’re making progress on it, but we just need a little more time to make sure it’s totally good,’’ Webb said.

The right-hander is confident the injury will heal quickly.

‘‘There’s no concern,’’ he said. ‘‘The MRIs are all good. I mean, if there’s no structural damage, there’s nothing to worry about.’’

The Diamondbacks said they would make a corresponding roster move before Monday’s game against St. Louis.