Manager Joe Torre said the uncertainty over Jonathan Broxton and his sore right big toe, and the fact that Ronald Belisario pitched each of the three previous games and was not available Friday night, prompted the move to "get us through the weekend."
Broxton tested his toe with a few throws off the bullpen mound during batting practice, and trainer Stan Conte said the closer might be available for the first Freeway Series game. Broxton missed the previous two games after receiving a cortisone injection for an inflamed nerve in the toe.
Torre said he told McDonald the promotion was temporary "as of now," because there are three disabled pitchers -- Eric Milton, Will Ohman and Eric Stults -- who figure to return soon.
"I didn't want him to think it was an audition for him," said Torre.
McDonald, so impressive last September and October, made the Opening Day roster as the fifth starter primarily off that memory, but pitched his way back to the Minor Leagues with a 6.75 ERA, experiencing command problems that followed him to Albuquerque until his last two starts.
He pitched seven innings each of his past two outings, allowing one earned run June 8 when he struck out 10, and no earned runs June 14 when he struck out 13. Over six starts, McDonald is 1-0 with a 3.26 ERA, 40 strikeouts and 14 walks in 30 1/3 innings.
McDonald credited Albuquerque pitching coach Jim Slaton with "waking me up, he lit a fire under me" as far as his approach to pitching."
"I got away from my game and who I was as a pitcher," McDonald said. "I was losing focus at some point. I have to keep my focus on every pitch no matter what."
Catcher A.J. Ellis, who caught McDonald on June 8, said the biggest difference he noticed was McDonald keeping his head upright during his delivery after tilting it sideways when he arrived at Albuquerque.
Schlichting has made only two appearances since being recalled on May 31 when Stults went on the disabled list. He allowed one earned run in 2 2/3 innings.
Milton is eligible to come off the disabled list Sunday and might if the club uses Weaver and McDonald Saturday. Otherwise, he's likely to remain disabled and make a Minor League rehab start Sunday before rejoining the rotation as the fifth starter at the end of next week.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.