NEW YORK -- Yankees first baseman Anthony Rizzo will miss the remainder of the season with post-concussion syndrome.
"Anthony is going to be shut down for the year," New York manager Aaron Boone said before Tuesday night's game against Detroit. "I would say everything is going well. His most recent checkup was all of the things we're looking for as far as there's improvements and where he is, but still hadn't been cleared yet to play.
"So they want to do at least another checkup in probably another couple of weeks. So we were just kind of up against the clock, but he's continuing to work out. He's continuing to make all the right cognitive improvements."
Rizzo was placed on the injured list Aug. 3, more than two months after getting hurt May 28 when he collided with San Diego Padres star Fernando Tatis Jr. on a pickoff play.
New York initially said Rizzo had a stiff neck. He sat out a three-game series in Seattle before returning to the lineup June 2 at Dodger Stadium, but the three-time All-Star then went into an extended tailspin at the plate.
When he finally landed on the injured list early last month, Boone said Rizzo had recently told the club's training staff he was feeling foggy. He then underwent neurological testing that revealed cognitive impairment.
Rizzo and Boone both said they believed his concussion issues stemmed from the May collision with Tatis at Yankee Stadium. Rizzo passed Major League Baseball's concussion testing, but batted only .172 with one homer in 169 at-bats afterward.
Prior to the game against the Padres, he was hitting .304 with 11 home runs in 204 at-bats for a Yankees team that's fallen out of the playoff race since and into last place in the American League East.
"I think you have regret if something doesn't get diagnosed right away," Boone said. "So yeah, you always want everything to be [diagnosed], but that's not the reality sometimes. I think all the right things, the right steps were happening. So you can't go back. But sure, you would have liked right away [to have] been able to know exactly what he was going to start dealing with."
When he went on the injured list, Rizzo was considered week to week. He was given three supplements designed to treat concussions and permitted to participate in physical activity.
"I think he's in a good place and I think the doctors and he have seen the progress they wanted to see," Boone said. "So I feel like he's encouraged by where's at. We'll probably throttle back on some of the baseball activity just because there's no need now. But I was in the gym with him earlier and he's getting after it. He's doing well."
Boone is optimistic Rizzo's concussion issues won't linger for the rest of his career. The 34-year-old signed a $40 million, two-year contract with the Yankees last November that includes a $17 million team option for 2025 with a $6 million buyout.
"I don't want to speak out of turn, especially when we're talking the seriousness of head injuries and whatnot," Boone said. "But my understanding is the last month as he's seen the specialist and the things they're asking him to do, I think everyone's been really encouraged by how he's done, and he continues to improve. So hopefully that's not the case."
A four-time Gold Glove winner, Rizzo helped the Chicago Cubs to a World Series title in 2016 that ended their 108-year championship drought.
He finishes this season batting .244 with 12 homers, 41 RBIs and a .706 OPS, by far his worst numbers since compiling a .523 OPS in his first 49 major league games with San Diego in 2011.
"He's been kind of a model of consistency in what's been a really good career," Boone said. "So I think the fact that we can trace it I think obviously got everyone's attention that, you know, initially is alarming -- but also like, OK, there's probably a reason here now that you weren't the player you've been really your entire career. Now I think the things that he's doing and the tools that we now have that I think help guys that have been through something like this should put him in good footing moving forward, is the hope."