That was especially true in light of the way Marcum had performed up to that point for the struggling Blue Jays, who have lost four in a row. Marcum had kept pace with Boston's Clay Buchholz, escaped a handful of dicey turns and limited the Sox to just one run over seven innings -- this after they churned out 13 runs on 18 hits one night earlier.
Marcum -- still searching for his first Major League victory since September 2008 after missing all of last season with a right elbow injury -- tried to convince Gaston to allow him to pitch a little longer. Marcum's pitch count had climbed to 103, though, and Gaston preferred to turn to his late-inning specialists.
"I understood the situation," Marcum said. "I told him I had more left, but he's the manager. That's his call. Either way, I would've been fine with it. Being a competitor, you want to go out there and pitch as much as you can, especially on a day like today where the bullpen has been getting used a lot lately."
With Marcum watching from Toronto's bench, Gaston handed the ball to Scott Downs in the eighth inning. Downs struck out Marco Scutaro to open the frame, but the left-hander then allowed back-to-back singles to Dustin Pedroia and Victor Martinez, and later issued a two-out walk to J.D. Drew to load the bases.
With the game stuck in a 1-1 deadlock, the Jays (10-11) turned to Gregg.
The Red Sox called upon Lowell as a pinch-hitter for David Ortiz.
"You've got to make him earn his way on base right there," Gregg said.
Gregg opened with a 86-mph slider, which broke sharply and sailed well outside for a ball. The right-hander followed with another slider -- one that tailed out of the strike zone even farther. Needing a strike, Gregg then fired a 92-mph fastball that hit the dirt and was gloved by catcher John Buck for a third ball.
Gregg had not issued a walk all season and knew he was still one pitch from escaping unscathed.
"Falling behind the guy is not really my concern," Gregg said. "My concern is executing the pitch at hand and getting an out."
His next pitch -- another 92-mph fastball -- popped into Buck's mitt just off the outside corner. Lowell dropped his bat and jogged to first base. Pedroia headed home from third base, crossed the plate and put the Blue Jays behind, 2-1. Four pitches later, Gregg caught a hard line drive off the bat of Adrian Beltre to end the inning.
But the damage had been done.
"That's why I have the job I do," Gregg said. "They trust that I'm going to come in and throw strikes in that situation."
The Jays did strike first in this one, grabbing a 1-0 lead on an RBI double from Vernon Wells in the first inning. That was the extent of the offense that Buchholz permitted during his eight innings on the mound, though. The young Red Sox righty scattered seven hits and kept the Jays without a hit in six tries with runners in scoring position after Wells' hit.
That put extra pressure on Marcum, who underwent reconstructive elbow surgery following the 2008 season. Boston (10-11) broke through against Marcum with two outs in the second inning, when he walked Ortiz and later yielded a game-tying single to Jeremy Hermida. From there, Marcum settled in and blanked Boston's lineup.
But as Gaston pointed out, Marcum had "nothing to show for it."
Marcum has logged at least six innings in each of his five starts, at least seven on four separate occasions and the right-hander has four no-decisions (with a 2.89 ERA in those outings) and one loss for his efforts. In fact, Marcum has logged the most innings (34) of any big league pitcher without a win this season.
"You can't say enough about what he's done out there for us each time he's taken the ball," Gregg said. "Hopefully things even out as the season goes along."
Marcum simply shrugs off his tough luck.
"There's going to be days when we'll come out and score a bunch of runs," he said. "Then there's days that you don't. That's baseball and that's life on a baseball field."
More concerning is the recent woes of the relief corps.
Over the past four games, the Blue Jays' bullpen -- billed as the team's strength entering the season -- has allowed 18 runs over a span of 11 innings, upping the group's season ERA to 5.65. In three of the team's past five defeats, including Tuesday's setback against the Red Sox, Downs has been hung with the loss.
It has been a disconcerting development for the Blue Jays.
"It's not like people are trying to walk people," Gaston said. "Those two guys [Downs and Gregg] have done a good job for us. Unfortunately tonight, we had it set up properly and it just didn't work out."