But Nathan bounced back from allowing a ninth-inning home run and the Twins fought back from a two-run deficit for a 5-4 victory over the Cleveland Indians on Tuesday.
Minnesota improved to 2-0 since losing first baseman Morneau for the season and pulled within 4½ games of first-place Detroit in the AL Central.
Nick Punto had three hits and two RBI for the Twins, who still have a daunting task to catch Detroit with only 18 games left -- seven against the Tigers -- without Morneau, a former AL MVP who has a stress fracture in his back.
"Morneau is a luxury, he's as good as they get, but we can't just lay down," Minnesota manager Ron Gardenhire said. "We know that we have to do other things. When you lose a power guy like that you have to figure out other ways to get it done, that's all."
The Twins got four hits, three RBI and two runs from the bottom third of their order and 2 2/3 scoreless innings of relief from their bullpen before Nathan gave up the solo homer to Matt LaPorta with one out in the ninth. Nathan walked Trevor Crowe with two outs, but got Michael Brantley to fly out for his 40th save in 45 chances.
Nathan reached 40 saves for the third time in his career and for the first time since recording 43 in 2005.
"It's been a while, but it feels good," Nathan said. "But we still know we've got some work to do. We still know if we're 4½ back we're going to have to do something special. We've got to win probably more than four games against [the Tigers], probably five to have even a glimpse of hope."
The deficit had been 5 1/2 games for six straight days, but the Twins beat Fausto Carmona (3-11) for the third time this season to finally trim the margin.
Carmona, coming off a season-low outing in which he allowed five runs while only getting two outs against Texas on Sept. 9, had some tough luck to start the decisive sixth inning.
Delmon Young's leadoff chopper off the Metrodome turf stayed high enough to tip off Jhonny Peralta's glove and slowly rolled to the outfield for a double.
"That shouldn't have been a double," Cleveland manager Eric Wedge said. "At the very least, he has to catch that ball. Ideally he catches it and makes a throw and it's going to probably be a close play."
Buscher followed with a single to score Young, and Buscher scored two batters later on Punto's second RBI single that chased Carmona.
The right-hander fell to 1-5 since he was recalled from Triple-A Columbus on July 31. He allowed five runs, nine hits and three walks in 5 1/3 innings.
"I'm never going to feel frustrated," Carmona said through an interpreter. "I know I'm a winner. Things are not working out good right now, but I'm never going to put my head down. I'm always going to look forward to my next start. Whatever happens, I'm going to continue to go forward."
Punto drove in Buscher in the fourth to cut what had been a 3-1 deficit to one run, and Orlando Cabrera's solo homer leading off the fifth tied the score.
Cleveland had a three-run fourth inning off Twins starter Scott Baker -- who entered the game 4-0 with a 0.93 ERA in four starts against the Indians in 2009. Peralta and LaPorta both singled home a run in the inning and Andy Marte added a sacrifice fly. Baker would allow no more runs, striking out five in 5 1/3 innings.
"We need everyone," Rauch said. "That's the kind of guys and kind of character that's on this team, guys are going to step up and do what they need to do. Buscher, Punto, all these guys who have been scrappy players and are getting opportunities and doing their best and doing their job."
- Along with Morneau, third-baseman Joe Crede is likely out for the season with back problems, and recent call-up Justin Huber is day to day with a strained oblique. But Gardenhire said his desire to call up reinforcements was "squelched" by the front office. Gardenhire would like to see one of the organization's top infielders promoted, but Luke Hughes and Trevor Plouffe are playing in the World Cup in Europe, while Danny Valencia and Brock Peterson are not on the 40-man roster.
- Baker finished with a 1.57 ERA against Cleveland in five starts this season.
- Carmona fell to 0-3 with a 7.91 ERA in four starts against the Twins in 2009.