NEW YORK -- Only seven days after returning from a two-month stint on the injured list, New York Yankees slugger Giancarlo Stanton is heading back on the shelf. Stanton exited Tuesday night's win over the Blue Jays (NYY 4, TOR 3) in the fourth inning with what was originally called a right knee contusion.

The injury occurred while Stanton ran the bases in the first inning. Here's video of the play. Stanton said he is unsure if he got hurt sliding into second base, or during the collision with Clayton Richard at third base.

The Yankees sent Stanton for tests following Tuesday's game and, Wednesday morning, manager Aaron Boone announced everything initially checked out well. He said Stanton had a bruise but no significant damage to the knee. Because the team has so many upcoming off-days due to their weekend London Series trip, they did not intend to put Stanton on the injured list.

"Tests were good," Boone said Wednesday morning. "He came in today -- there's no swelling in there -- sore and stiff. He is going through treatment now. So nothing as far as any moves or anything like that. We're just kind of seeing how the next couple hours unfold, and even the next couple days, but no move or anything."

At some point during Wednesday's win (NYY 8, TOR 7), everything changed. Boone announced Stanton would indeed be placed on the injured list following the game, and will not accompany the team to London. A follow up examination revealed a posterior cruciate ligament sprain in the knee. Stanton will be reevaluated in 10 days.

"Giancarlo is going on the IL," Boone said following Wednesday's game. "He was examined right before the game with (team doctor) Dr. Ahmad, and in conjunction with the physical exam and looking at the MRI, there's a PCL sprain in there. He is not going to go (to London), he will go on the IL. And we'll reevaluate him in 10 days."

MLB: Tampa Bay Rays at New York Yankees
Giancarlo Stanton has spent nearly the entire 2019 season on the shelf. USATSI

Stanton missed two months with various injuries earlier this year -- he had a biceps injury that led to shoulder trouble, then a calf issue as well -- and he returned just last week. He went 6 for 22 (.273) with a double and a home run in five games between his injured list stint and this new knee issue. This will be only his second injured list trip this year, but it is his fourth injury.

"He's going on the IL, I didn't necessarily expect that. I think it explains the pain he was in when he came in," Boone added. "Frustrated for him knowing how much he's worked to get back and the couple of setbacks he's had along the way. Felt like he was starting to get in a groove with us a little bit. We got to deal with it and hope to get him right at some point."  

Even with the surprisingly productive Cameron Maybin on the injured list, the Yankees are deep in outfielders. Aaron Judge returned from his oblique issue last week, plus the Yankees have Clint Frazier in Triple-A. Mike Tauchman will replace Stanton on the 25-man roster and take over as the fourth outfielder with Brett Gardner returning to the starting lineup.

The Yankees begin the two-game London Series with the Red Sox on Saturday. Between the London Series and the All-Star break, the Yankees will play only eight games in the next 15 days. Stanton could return soon after the All-Star break and, all things considered, he not miss many actual games on the field.

"Obviously when he's going well (he's) one of those are guys that can impact a game in a profound way and carry a club when he's rolling hot," Boone said. "Hopefully it's not something that's too long and we get him back up and running soon, because I feel like over the last couple of days the timing and the at-bats have been really good. Hopefully this is a small bump in the road."

In eight games this season Stanton is 8 for 30 (.267) with one home run. Despite his injury -- and all their other injuries -- the Yankees are 51-28 following Wednesday's win and have a season-high 6 1/2-game lead in the AL East. Still, the sooner they get Stanton back and keep him healthy, the more dangerous they will be.