"When they started walking around on the back of the mound, you know something's wrong," Gaston said on Friday night.
Halladay felt a sharp pain during his second pitch of the inning -- a 93-mph fastball fouled back into the stands by Marlins right fielder Jeremy Hermida -- and was quickly met on the hill by Gaston and head trainer George Poulis. When the discomfort persisted during a warmup pitch, Halladay retreated to the training room with a strained right groin.
In the aftermath of Toronto's 7-3 Interleague loss to Florida, the primary concern was Halladay's health. He spent the final six innings of Friday's game icing his leg and receiving treatment from Toronto's medical staff. Halladay said later that he would leave it up to Poulis' team to determine whether the pitcher will undergo an MRI exam on Saturday.
"That's in George's hands," Halladay said. "I know he's talking to the doctors and, hopefully, when I get in tomorrow, we'll have some kind of game plan. As of right now, I'm kind of letting George handle it and talk to the doctors and figure out the best way to move forward. I'm kind of just doing what I'm told."
Halladay -- who leads the Major Leagues with 10 victories -- will likely be instructed to skip at least one turn in Toronto's rotation. Helping matters is the fact that the Blue Jays have an off-day on Monday. Even with that extra day, though, there is a realistic chance that Halladay will miss his next start, which was scheduled for Wednesday in Philadelphia.
In that scenario, Gaston indicated that right-hander Scott Richmond would likely get the nod on the road against the Phillies. On Friday, Richmond relieved Halladay in the top of the fourth inning and then proceeded to log 3 2/3 innings. The Jays will know more on Saturday, but Gaston is hoping to have Halladay back in the fold as soon as possible.
"I hope it's one [start]," Gaston said. "Whatever we can do to get him back."
The Blue Jays could ill-afford to lose Halladay, who captured the American League Cy Young Award in 2003 and was the runner-up for the honor a year ago. This season, Doc is on pace to be a leading candidate to start for the AL in the All-Star Game in St. Louis next month and, at his current pace, Halladay would also be a strong contender for another Cy Young.
Entering Friday's start, Halladay was riding a streak of seven wins in a row and had logged at least seven innings in each of his previous 13 outings. The right-hander led the Majors in wins and innings (100), was tied for the lead in walks per nine innings (1.1), second in complete games (three) and ranked third in the AL in strikeouts (88) and fifth in ERA (2.52).
Prior to his injury-shortened start against Florida, Halladay had gone 7-0 with a 2.03 ERA, 62 strikeouts and nine walks over 71 innings over his previous nine trips up the hill. He was coming off two consecutive complete games and hadn't lost a start since May 21. The run Halladay surrendered in the first inning of his no-decision against Florida also snapped a streak of 11 straight shutout innings.
"You hate to see a guy with that kind of dominating stuff leave the game," said Marlins center fielder Cody Ross, who grounded out in his lone at-bat against Halladay. "He's good for the game. He's good for baseball, and we obviously hope he's not hurt too bad."
Halladay feels the same.
The horse of Toronto's staff said he has never had a groin issue before and the injury snuck up on him against the Marlins. Halladay added that he had no indication of it in the first three innings, in which he allowed one run on five hits, that something anything was wrong. Doc didn't feel anything until the second pitch to Hermida in the opening at-bat of the fourth.
"It wasn't a lot of pain right after, so I was kind of hoping it was just a twinge or something," Halladay said. "But, I felt it on the next pitch. It's just one of those things that kind of out of nowhere catches you off guard. Hopefully, we find out exactly what's going on and go from there. Obviously, the hope is that it's nothing major."
With more than three months left on the schedule, it made sense for the Blue Jays to take precaution with Halladay and have him leave the game. Even if it were later in the season, though, Halladay wasn't sure if he would be able to pitch through this particular injury.
"No, I don't think I could've gone with it at that point," he said. "But, I don't know."
One positive is that Halladay does not feel much pain while walking -- he walked off the field with Poulis without limping and appeared fine while making his way into the clubhouse. Halladay did say that the injury did flare up during a few of the initial tests performed by Toronto's training staff.
Halladay's setback comes after news broke Tuesday that Blue Jays starter Jesse Litsch is scheduled to undergo season-ending Tommy John ligament replacement surgery on his right elbow. Toronto also opened the year without injured starters Shaun Marcum (right elbow) and Dustin McGowan (right shoulder), who could both potentially be out until 2010.
Right-hander Casey Janssen -- currently in the rotation -- opened the season on the disabled list after missing all of last year with a right shoulder injury. Rookie left-hander Ricky Romero, who made the Jays' Opening Day roster as the fourth starter, also spent time on the shelf earlier this season with a right oblique strain.
"It happens, unfortunately," Halladay said of the rash of injuries. "You don't want to have it too much, but hopefully it's not anything that's going to cost me a lot of time, and we can move forward. It's just part of the game and, I think everybody, you learn to adapt and kind of try to take those things in stride and move on."
Jordan Bastian is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.