McDonald, called up from the minors earlier in the day, hit a pinch-hit two-run homer in the eighth inning to tie the game and won it with an RBI single in the ninth to lift the struggling Red Sox to a 7-6 comeback win over the Texas Rangers on Tuesday night.
"I don't care how we did it. We desperately needed to win a game," Boston manager Terry Francona said. "We hung in there and won a game that we definitely needed to win."
The Red Sox snapped a five-game losing streak despite allowing the Rangers to steal a club record nine bases. Texas has dropped five straight.
McDonald, 31, signed as a minor league free agent on Nov. 24, finished last season with Cincinnati and was a non-roster invitee to the Red Sox camp.
"I couldn't write a script any better than this," he said. "A lot happened. A dream come true. That's why I signed over here to be able to play in this type of atmosphere."
He was the first Red Sox player to homer in his initial plate appearance since Orlando Cabrera did it on Aug. 1, 2004, at Minnesota.
Kevin Youkilis opened the ninth with an infield hit off the body of Frank Francisco (2-3), advanced on a passed ball and was sacrificed to third by Bill Hall. After Mike Lowell was intentionally walked and Adrian Beltre popped to first, Jason Varitek then walked on four pitches before McDonald lifted a fly ball that scrapped the Green Monster just over the leap of Josh Hamilton.
He was mobbed in short left field as the Rangers trotted off.
"They got me pretty good out there," he said, still beaming.
Nelson Cruz and Elvis Andrus each had three of Texas' club record nine stolen bases as the Rangers opened a 6-1 lead after five innings.
"We didn't figure out a way to shut the game down," Rangers manager Ron Washington said.
Jonathan Papelbon (1-1) pitched a hitless ninth for the win.
The Rangers swiped all nine against knuckleballer Tim Wakefield and catcher Victor Martinez.
"I was just concentrating on throwing strikes and wasn't keeping an eye on the running game, which showed, they stole nine bases off me," Wakefield said. "I know it'll get better."
Texas stole one in the first, five in the third and two in the fourth. Cruz set the club record with his third of the game, swiping third in the fifth.
"If we got one base, of course, we were going to run -- a knuckleball, tough to handle," Washington said.
Josh Reddick, recalled earlier in the day from Triple-A, had a two-run double for Boston, cutting the deficit to 6-4 in the sixth.
The Rangers were 18 for 18 in stolen-base attempts against the Red Sox last season.
The previous club record was eight, set against Boston in Arlington, Tx. last August 15.
Cruz started the Rangers' running game in the first when he had an RBI single to make it 1-0 and followed by stealing second.
Martinez's RBI single in the first tied the game. Boston had gone 0 for its last 32 with runners in scoring position.
Texas set a club record for steals in an inning with five in the third. Hamilton's grounder scored Andrus to make it 2-1. Andrus walked leading off, then stole second and third. Vladimir Guerrero had a pair of stolen bases and Cruz the other in the inning.
Julio Barbon's RBI single triggered a three-run fourth. Joaquin Arios scored on a wild pitch and Michael Young added a run-scoring single, making it 5-1.
Before the inning, Martinez threw the ball into center field while warming up Wakefield. He also threw it past the pitcher in the fifth inning.
Boston's catchers have thrown out just one of 31 runners this season.
The nine steals allowed matched the most by Boston since Oct. 3, 1913.
Hamilton overran Reddick's fly ball down the line; that fell in for a double to make it 6-4 in the sixth. The ball appeared to bounce back into play off a fan.
"I just misplayed it," he said.
Rangers starter Colby Lewis allowed three runs on five hits in five innings. Wakefield gave up six runs on seven hits in six innings.
NOTES: Cruz left the game in the ninth with a cramp in his left hamstring. ... The Red Sox put outfielders Mike Cameron (strained abdominal muscle) and Jacoby Ellsbury (bruised chest) on the 15-day DL before the game. They recalled Reddick and selected McDonald from Triple-A Pawtucket. ... Wakefield surpassed Cy Young to move into second place on the Red Sox all-time list with more than 2,729 innings pitched.