Halladay was making his first start off the disabled list, following a two-week fight with a mild groin strain. He came back in fine form in a 4-1 loss to the Rays at Rogers Centre, but Gaston pulled the plug on Halladay's outing after just six innings and 88 pitches.
Gaston simply did not want to risk seeing his horse suffer a setback.
"He had a couple long innings out there, so I just thought that was enough for him," Gaston explained.
The Rays, who moved past the Blue Jays for third place in the American League East over the weekend, were counting their blessings. Tampa Bay was struggling to solve Halladay in a game that was shaping up to be like many of the past contests he's attempted to finish on his own.
Instead, Halladay was forced to watch the Rays add a pair of insurance runs off Toronto's bullpen -- more than enough support to back a strong outing from Tampa Bay rookie Jeff Niemann. The loss was the fourth in the past five games for the Blue Jays (41-37), who are now 6-10 against the AL East this season.
The Jays hoped Halladay could help end their recent woes. The Rays (43-35) were happy that didn't happen.
"Thank God he's been off for two weeks," Tampa Bay manager Joe Maddon, "because they would have left him in there longer. He would've probably finished that thing off. I'm sure they had to be worried about conditioning and the potential to hurt the arm after such a long layoff.
"We had that working in our favor."
Also helping the Rays' cause was the presence of left fielder Carl Crawford -- a nemesis of the Blue Jays and Halladay over the years. Halladay (10-2) said the time on the DL did not harm the effectiveness of his pitches, but there was one ill-fated curveball that the right-hander left dangling up in the strike zone to Crawford in the third inning.
B.J. Upton drew a walk from Halladay to open the frame, and then proceeded to steal second base and advance to third on a throwing error from Jays catcher Rod Barajas. With Upton standing 90 feet from home plate with no outs and no runs for either team at that point, Halladay threw a 1-1 breaking ball that stayed up and headed inside to Crawford.
Crawford took advantage, pulling the misplaced offering to right field, where it soard high and crashed deep into the second deck for a two-run homer that put Toronto behind, 2-0.
"I just made a poor pitch," Halladay said. "It just has to be down more, really. He's a pretty good breaking-ball hitter when it's closer to him, especially if you leave it up."
Crawford finished the game 2-for-3 with two RBIs and one stolen base and a walk. Against the Blue Jays, he has hit .323 in his career, collecting 15 doubles, seven triples, 15 home runs, 59 RBIs and 46 stolen bases in 106 games along the way. Perhaps more impressive, Crawford has hit .318 with two homers and nine RBIs against Halladay.
Even with his strong showing on Monday, Crawford said it didn't look like Halladay was affected by the stint on the disabled list.
"He still looked kind of sharp -- he was hitting spots," Crawford said. "It didn't look too different. It wasn't like you saw a big difference. He probably wasn't his best, but it wasn't a big difference."
Halladay said the only real difference was some spotty location in the first three innings, when he allowed four hits and issued two walks. Halladay, whose season ERA rose to 2.56 in his first loss since April 21, finished with seven strikeouts and induced six groundouts.
"For the most part, I felt pretty good with everything," Halladay said. "I was just focusing on hitting spots. I've thrown in the bullpen and everything was fine, so I didn't feel like I hadn't thrown in a long time. I think it's just a matter of the consistency sometimes, falling behind guys. Other than that, I felt good."
Halladay noted that the groin injury that sidelined him for the past two weeks did not present any problems.
"That wasn't a concern for me," Hallladay said. "It was, 'Go out and pitch like normal.' I wasn't worried about keeping it loose. I feel like that's something that's over and done with. That really wasn't a concern. I think you approach it like any other start. Once you feel like you're over it, you don't look back. You continue to go out and pitch."
It wasn't like any other start, though.
Prior to Monday's outing, Halladay had logged at least seven innings in each of his starts with the exception of the injury-shortened appearance on June 12. Halladay has three complete games and had gone the distance in consecutive starts before tweaking his groin in his last start against the Marlins.
In the seventh inning, Gaston decided to turn to right-hander Jeremy Accardo, who allowed a solo home run to Tampa Bay's Pat Burrell and later gave up a run-scoring sacrifice fly to Upton. The Jays made a brief rally in the eighth, managing a run on a single from Barajas, but that was the extent of Toronto's scoring against Niemann during his 7 1/3 innings.
Next time, Halladay will probably be allowed to stay on the mound. Right now, Gaston is just thrilled that he's healthy.
"He's good. That's the good news," Gaston said. "I just felt like that was enough pitches."
Jordan Bastian is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.