d'Arnaud has been out of action since Alfonso Soriano's backswing caught him on the head May 13. Collins indicated d'Arnaud, once he passes all of the required tests, won't be held back.
"When he's ready to play, he'll be back in there," Collins said.
Left-handed batter Juan Centeno and right-handed batter Anthony Recker have platooned in d'Arnaud's absence. Centeno, who is 3-for-10 with a walk in three games, has been "fine," in Collins' eyes.
"He's handled the bat good. He's a defensive little guy," Collins said. "He's lived up to everything we've seen in the past. He's not a big power guy, but he puts the bat on the wall. He's done fine."
Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. Tim Healey is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.