Morneau, who said he has not been able to feel the index finger on his left hand since the last week of Spring Training, will have neck surgery on Wednesday to relieve a pinched nerve causing the problem. The procedure will remove a herniated disk fragment from Morneau's neck.
"When we immobilized his wrist, it was the expectation and hopes of our doctors that the time off from swinging would also benefit his neck," Twins head trainer Rick McWane said. "Last week we sent him to see another neck specialist; this was our desire, our team doctors' desire. It wasn't something that Justin was pushing.
"That doctor decided that the best course of action would be to have surgery."
McWane said it was a non-invasive procedure, but Morneau, who has been on the 15-day disabled list retroactive to June 10, was expected to be out at least six weeks after Wednesday's surgery.
McWane also emphasized several times that it was the decision of the team doctors to have Morneau see a neck specialist, and that Morneau would have preferred to fight through it. After seeing the specialist, it was determined that surgery was the best option.
Morneau also had the cast put back on his left wrist to keep it immobilized, which will help that injury heal while he's unable to do anything baseball-related due to the neck surgery.
"The thing that kind of made the decision was hearing that it could be permanent weakness in the arm, and numbness in the fingers and all that stuff," Morneau said. "I'd like that to go away. That's the plan for the surgery, hopefully that'll be the result and I'll come out good and be ready for August and September.
"That's what I think the decision came down to, being able to play late in the year instead of trying to find a way to push through it and not feel very good. I could break down and need the surgery later in the year and have to sit out again."
With Morneau out, Luke Hughes and Michael Cuddyer will likely split most of the time at first base until he returns. Twins manager Ron Gardenhire did suggest that a number of others could be options there as well, including catchers Rene Rivera and Joe Mauer.
"I'm trying everything," Gardenhire said. "I've talked to Joe about it, I've talked to everybody about it. We're not afraid to move people around and keep his bat in the lineup on a more everyday basis. Playing a little here, playing a little there."
After returning from a concussion that cost him much of last season, Morneau has struggled through the first three months of this season, fighting through neck and wrist injuries. The result has been a .225 batting average, with four home runs and 21 RBIs through 55 games.
Morneau missed five games in early April with an injury, and has not played since June 9 due to the wrist injury that landed him on the DL. McWane said that the neck injury and the concussion were not related in any way.
It's the latest in a number of injuries for Morneau in recent years. He missed the last few weeks of the 2009 season with a stress fracture in his back, and the second half of 2010 with the concussion suffered on July 7 at Toronto.
"It's just sort of, trying to figure out if I'm doing something wrong, if there's something wrong mechanically, if there's something wrong training, whatever," Morneau said. "I'm trying to look at everything to see if there's anything I can do differently, or better or less or whatever it is.
"As frustrating as it is for fans to sit there and go, 'You know, I'd like to see this guy play,' it's a million times more frustrating for me to have to sit here and watch it on TV and not be a part of it."
The latest setback for Morneau comes just as the Twins were seemingly on the verge of getting their entire Opening Day lineup back healthy.
Designated hitter Jim Thome rejoined the club in Milwaukee and is expected back soon, which should help replace some of the power lost without Morneau in the lineup.
"You want them to get back as quick as they can," Thome said. "[But] I think when you look at our season, and how our season's gone, you've really got to look at our young guys and how they've stepped up."
Jordan Schelling is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.