The All-Star catcher wasn't in the starting lineup because he caught the previous two days while rehabilitating his throwing shoulder at extended spring training in Florida. Posada had been out since April 28 with right rotator cuff tendinitis.
"I don't think it's going to be 100 percent, but it's good enough," he said. "I think it's good enough to get going."
New York manager Joe Girardi said Posada will catch two games in a row sometime within the next four days.
"We're just going to have to watch Jorgie," Girardi said. "We need to know that he is completely healthy, 100 percent.
"He definitely brings an attitude to the park every day, and I like that," the manager added. "That fighting spirit."
Posada said he'll need surgery to repair his labrum after the season, similar to a procedure he had following the 2001 season.
"There's no discomfort. Something's messed up in there," Posada said. "We're going to have to get it fixed."
A longtime leader in the Yankees' clubhouse, the 36-year-old Posada signed a $52.4 million, four-year contract last offseason. He was batting .302 with one homer and 11 RBIs in 63 at-bats this year.
Posada's stint on the DL was the first of his major-league career, which began in 1995. His teammates were glad to have him back, and New York (28-30) is in dire need of his steady production.
"It's a little louder in here. That's probably the biggest difference," buddy Derek Jeter said with a chuckle. "Everyone knows what he means to the team."
Girardi said Posada had been texting or calling him every day lately, asking if he could return to the team "tomorrow."
"Tomorrow is here now, so I don't have to deal with that," Girardi said, adding that he's looking forward to finally having his entire projected lineup available.
Because of injuries, the Yankees have also played without Alex Rodriguez and Jeter for extended stretches this season.
To make room for Posada on the roster, New York optioned right-hander Dan Giese back to Triple-A Scranton/Wilkes-Barre. Giese was called up to pitch Tuesday night in relief of Joba Chamberlain, who was on a short pitch count in his first big-league start.
Giese allowed one run and five hits in 3 2/3 innings, taking the loss in Toronto's 9-3 victory.
In other news, first baseman Jason Giambi was not in the lineup because of a sore left foot but was available to pinch-hit, Girardi said.
"It's still a little sore and there's a tad bit of swelling," Giambi said through club spokesman Jason Zillo.
Giambi was hit on the top of his foot by a pitch Wednesday night.
"I would expect him to be fine tomorrow," Girardi said.