"You can't cost your team games trying to learn a job," Schilling said. "You can't do that. There's no excuse for what happened."
Schilling (4-5) entered the game with a two-run lead with two outs in the eighth and struck out Curtis Granderson to end the inning. In the ninth, Schilling gave up three runs on four hits and a walk.
The six-time All-Star was moved from ace to closer a month ago when he returned from an ankle injury. He was out for 2½ months with a bone bruise on his right ankle, the same damaged ankle he pitched on in the AL championship series against New York and the World Series against St. Louis.
Schilling had converted nine saves in 10 opportunities, but had given up four runs on four hits -- including three homers -- in his last two appearances.
"He's not the Curt Schilling that finished last season," teammate Johnny Damon said. "He needs some work, he knows it. He'll find it. Hopefully, he'll get another opportunity (Tuesday) and he'll close it out for us."
Placido Polanco started the rally with a leadoff single in the ninth, Dmitri Young followed with a one-out RBI triple and Magglio Ordonez tied the game with a single. After a walk and a strikeout, McDonald singled to left and as the Tigers celebrated at home plate, Schilling walked toward the dugout visibly dejected.
McDonald was beaming while talking about the most important hit of his career. The utility infielder, acquired last month from Toronto, has bounced between the majors and the minors since his major-league debut with Cleveland in 1999.
"It's been a lot of years of playing baseball to finally feel that," he said. "I've watched a lot of guys get that feeling. I'll remember that for a long time."
McDonald entered the game in the ninth only because Omar Infante made a baserunning mistake, not running hard on a grounder that went from foul to fair territory down the third-base line, leading to the second out of the eighth inning.
"Those are lessons that we need to learn," Tigers manager Alan Trammell said. "I made my statement. I talked to him. It's over."
Jamie Walker (4-3) pitched the ninth for the Tigers, who have won three straight and snapped Boston's six-game winning streak.
The AL-East leading Red Sox appeared to be on their way to another victory behind David Ortiz's 29th home run and Alex Cora's three RBI, two on a homer, before Schilling struggled.
Red Sox starter Bronson Arroyo gave up three runs on 10 hits and no walks over six innings.
"He battled and kept us in that game," catcher Jason Varitek said. "We just couldn't break it open."
Tigers starter Sean Douglass allowed five runs on five hits and four walks over four-plus innings.
Cora's two-run homer put Boston ahead 3-0 in the second after Manny Ramirez doubled and scored on Bill Mueller's sacrifice fly. Infante pulled Detroit within a run with a two-run double in the home half, and Ordonez's sacrifice fly in the third tied it.
Cora's groundout in the fourth scored Ramirez. Ortiz's RBI double gave the Red Sox a 5-3 lead in the fifth, and his homer in the seventh made it 6-3.
|Pinch-hitter John McDonald finishes off Schilling and the BoSox with his two-out single in the ninth. (AP)|
|Players of the Game|
|Boston Red Sox|
|Johnny Damon, CF||4||1||0||0||1||0||1||.334|
|Edgar Renteria, SS||5||0||1||0||0||0||0||.281|
|David Ortiz, DH||5||1||2||2||0||1||0||.303|
|Manny Ramirez, LF||3||2||1||0||1||0||0||.287|
|Jason Varitek, C||3||0||1||0||1||0||1||.305|
|Roberto Petagine, 1B||3||1||0||0||1||0||3||.286|
|Bill Mueller, 3B||3||0||2||1||0||0||0||.292|
|Alex Cora, 2B||4||1||1||3||0||1||1||.218|
|Gabe Kapler, RF||4||0||0||0||0||1||3||.308|
|2B - David Ortiz (33, Douglass), Manny Ramirez (22, Douglass), Bill Mueller (24, Colon)|
|HR - David Ortiz (29, Colon), Alex Cora (3, Douglass)|
|SF - Bill Mueller (4)|
|RBI - David Ortiz 2 (101), Bill Mueller (48), Alex Cora 3 (14)|
|2-OUT RBI - Alex Cora 2 (5)|
|Team LOB - 6|
|Boston Red Sox|
|Mike Timlin (H,24)||1||0||0||0||0||1||0||1.39|
|Chad Bradford (H,5)||0.2||2||1||1||0||1||0||3.09|
|Curt Schilling (BS,2; L,4-5)||1||4||3||3||1||2||0||6.69|
|Pitches-Strikes - Bronson Arroyo 107-73, Mike Timlin 16-12, Chad Bradford 18-13, Curt Schilling 26-16|
|Ground Balls-Fly Balls - Bronson Arroyo 7-9, Mike Timlin 1-1, Chad Bradford 1-0|
|Batters Faced - Bronson Arroyo 28, Mike Timlin 3, Chad Bradford 4, Curt Schilling 8|
|Placido Polanco, 2B||5||1||2||0||0||0||2||.326|
|Chris Shelton, 1B||5||1||2||0||0||1||2||.322|
|Dmitri Young, DH||5||0||2||1||0||1||2||.263|
|Nook Logan, PR-DH||0||1||0||0||0||0||0||.266|
|Magglio Ordonez, RF||4||1||2||2||0||0||1||.305|
|Craig Monroe, LF||4||1||1||0||1||1||3||.283|
|Brandon Inge, 3B||5||2||2||0||0||1||5||.264|
|Omar Infante, SS||4||0||1||2||0||1||0||.231|
|John McDonald, SS||1||0||1||1||0||0||0||.284|
|Vance Wilson, C||3||0||2||1||0||0||0||.194|
|Curtis Granderson, CF||4||0||1||0||0||1||3||.308|
|2B - Chris Shelton (14, Arroyo), Omar Infante (23, Arroyo)|
|3B - Chris Shelton (2, Arroyo), Dmitri Young (3, Schilling)|
|SF - Magglio Ordonez (5)|
|SH - Vance Wilson (1)|
|RBI - Dmitri Young (57), Magglio Ordonez 2 (33), Omar Infante 2 (38), John McDonald (13), Vance Wilson (10)|
|2-OUT RBI - John McDonald (4), Vance Wilson (2)|
|Team LOB - 10|
|DP - Shelton-V. Wilson|
|E - Omar Infante (8, Wild throw)|
|Jamie Walker (W,4-3)||1||0||0||0||0||1||0||2.54|
|Pitches-Strikes - Sean Douglass 79-45, Roman Colon 58-37, Jamie Walker 11-7|
|Ground Balls-Fly Balls - Sean Douglass 5-6, Roman Colon 6-5, Jamie Walker 1-1|
|Batters Faced - Sean Douglass 21, Roman Colon 15, Jamie Walker 3|
|Attendance - 30426|
|Game Time - 3:08|
|Temperature - 78|
|Umpires - Home - Bob Davidson, First Base - Andy Fletcher, Second Base - Paul Schrieber, Third Base - Jeff Kellogg|