It was the Twins' third walk-off win of the season and the first on a walk-off fielder's choice.
The ninth-inning dramatics came after Nathan suffered his first blown save of the year. He gave up a leadoff home run to pinch-hitter Ben Zobrist on a first-pitch fastball in the top of the ninth.
But the Twins quickly turned Nathan into the game-winning pitcher thanks to a rally off left-hander J.P. Howell in the bottom of the ninth inning.
With the game knotted at 3, Morales led off the frame with a single. Nick Punto's sacrifice put Morales in scoring position, and Denard Span's infield single moved the winning run to third base. After pinch-hitter Brendan Harris drew a walk, Morneau came to the plate. The Rays brought right fielder Ben Zobrist in for a five-man infield.
"If it works, it's a great formation," Twins manager Ron Gardenhire said. "But it didn't work this time."
It didn't work for the Rays because Morneau lined a short-hopper to Iwamura just a little too hard for the second baseman to handle.
Iwamura wasn't able to field the ball cleanly, and the double-play chance was foiled. Harris was ruled out at second, but Morneau, who was slotted as the Minnesota DH for the day, was able to beat out the throw to first easily as he hustled down the line -- making it a walk-off fielder's choice.
"We had it set up," Rays manager Joe Maddon said of the five-man infield. "That's something we work on. He hit it really hard; that's not an easy play for Aki by any means. It just bounced far enough away from him that permitted Morneau to beat it out."
Despite the unique defensive setup by the Rays, Morneau said he wasn't focused on the extra infielder while he was up at the plate.
"I didn't see those guys, and it didn't even matter where they were," Morneau said. "I was trying to hit something in the outfield. You can't worry about trying to sneak a ball through the hole there. My approach was trying to get something in the air. I ended up hitting the top of the ball, but I still hit it hard."
The club's lineup was able to pick up Nathan, but before the closer's blip, there were some other bright spots for the Twins in the contest.
Left-handed starter Francisco Liriano had been in line for his first win of the 2009 season prior to Zobrist's homer in the ninth.
Against the Rays, Liriano started to find the form the Twins have been expecting to see from the southpaw. He retired 11 of the first 13 batters he faced and held the Rays scoreless until the sixth inning, when they knotted the game at 2 on Evan Longoria's RBI double and Willy Aybar's sacrifice fly.
Those two runs came after the Twins already had given Liriano a 2-0 lead thanks to a two-run homer by Morneau in the first inning off Rays starter James Shields. The blast to left-center field was Morneau's fifth home run of the season.
But while the game was tied at 2 heading into the bottom of the sixth, the Twins were able to take advantage of rare control problems by Shields.
With two outs in the inning, Shields walked Michael Cuddyer to load the bases. He then hit Brian Buscher with a pitch to plate a run.
The Twins then were able to bridge the gap to Nathan in spite of being without Jesse Crain, who had been filling the setup role prior to going on the disabled list with shoulder inflammation.
On Tuesday night, it was left-hander Jose Mijares who proved to be reliable in a key situation. Despite walking Carl Crawford to start the inning and put the tying run on base, Mijares found a way to settle in after that. Even after Crawford stole second base on Evan Longoria's strikeout, the left-hander remained calm and got the next two batters -- Carlos Pena and Aybar -- to strike out as well.
"It's needed," Gardenhire said of Mijares' performance. "We'll need a lot more of that as we go along. That's what we were hoping going into Spring Training -- that he would be one of the guys. I think he's making us feel a little better about it."
And there was another positive for the Twins, although it's not one that will show up in any highlights or box score. It was the fact that Morneau didn't try the "Nick Punto approach" -- sliding headfirst -- to beat out the throw to first base on his game-winning play.
"When I was running up the line, I thought about it," Morneau said with a smile. "Then I thought better. ... It looked like I was going to be safe going up the line, so I figured [I should] take it easy on myself."