On the disabled list since May 5 with an intestinal virus, Richard was 0-4 with an 8.54 ERA in six starts before the ailment took hold. He went 0-1 with a 2.25 ERA, 12 strikeouts and no walks in 12 innings with Tucson while tinkering with a higher arm slot.
The Padres initially kicked around the idea of carrying an extra position player for their series in Arizona before opting to add another pitcher in Layne.
"As it turns out, we needed the extra arm," said Padres manager Bud Black. "Tommy came in and did a nice job for us."
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.