"It has bothered him the last four days," Girardi said. "I need to make sure he's 100 percent."
Posada and Blue Jays reliever Jesse Carlson were both disciplined for their roles in the eighth inning of New York's 10-4 loss to Toronto on Tuesday, serving three-game bans.
After two Blue Jays batters had been hit earlier in the game, Carlson threw a pitch behind Posada, prompting both benches to briefly empty onto the field and drawing a warning from home-plate umpire Jim Joyce.
Posada worked a walk against Carlson and scored in the inning on a Brett Gardner hit. As he returned to the dugout, Posada jutted an elbow at Carlson in what Joyce termed "unsportsmanlike" and "a cheap shot," leading to Posada's fifth career ejection and first since Aug. 24, 2007.
Because of the stiff neck, Posada was not to be in New York's lineup on Wednesday, and he agreed to serve a three-game suspension immediately. That left him unavailable for the first two games of the Yankees' series against the Mariners, as Jose Molina and Francisco Cervelli logged starts.
"I expect him to be fresh," Girardi said.
In other injury updates, right fielder Nick Swisher received a day off on Sunday, as Girardi said he is "banged up." Gardner started in center field, and Melky Cabrera got the nod in right.
Yankees left-hander CC Sabathia was sporting a bruise on the left side of his chest, the lasting effect of a Franklin Gutierrez line drive on Saturday, but the ace is not expected to miss his next start.
Additionally, right-handed reliever Dave Robertson (right elbow stiffness) played catch on Sunday at Safeco Field and will be cleared to resume throwing from the mound.
Pitching coach Dave Eiland is observing Robertson's progress and the Yankees' hope is that the rookie can get into at least two games before season's end to determine his viability for the playoff roster.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.