OAKLAND -- Clint Frazier's frustrating season effectively ended in a Pittsburgh medical office this week, as the Yankees outfielder has experienced a recurrence of the post-concussion symptoms that limited him to 15 big league games this year.
Frazier was rehabbing with Class A Advanced Tampa, preparing to join the Yankees' Double-A Trenton affiliate for its postseason run. Instead, he was sent for a consultation with Dr. Michael "Micky" Collins, who is regarded as a renowned expert in sports-related concussions.
"We're just trying to really hone in and get the best program we can in place for him to really start getting him back on the right track for good," Yankees manager Aaron Boone said.
Boone said Frazier has returned to Tampa, Fla., and it is now unlikely he will be able to play in additional big leagues games this year.
Frazier, who turns 24 on Thursday, initially sustained the concussion in late February while crashing into the left-field wall during a Grapefruit League game against the Pirates in Bradenton, Fla.
At one point during the spring, Frazier said he was having difficulty driving to the ballpark and had confused the names of his cats, Papi and Phoenix. He returned to concussion protocol in July, having attempted a diving catch while playing for Triple-A Scranton/Wilkes-Barre.
"It's been a year of trying to get our hands around exactly what's going on with him and trying to get him moving in the right direction with momentum," Boone said. "Hopefully this is a step in that direction."
In his second full year as a member of the Yankees organization, Frazier hit .265/.390/.353 with one RBI in 34 big league at-bats. He also played 48 games for Scranton/Wilkes-Barre and six for Tampa, hitting .305/.388/.562 in the Minors.
"We know there's a lot of talent that he possesses, and hopefully this gets him going in the right direction," Boone said. "We still believe he'll be a very important part of our franchise."
Help is on the way
Yankees shortstop Didi Gregorius is set to be activated for Friday's series opener against the Mariners in Seattle, Boone said. Gregorius has been on the disabled list with a left heel contusion since Aug. 19.
"In a lot of ways, he's one of the heartbeats of this club," Boone said. "He does so many things in the middle of the diamond, playing a premium position as well as he does. It gives us a lefty presence, usually somewhere in the middle of our lineup.
"The little intangible things that he does so well, just as far as always being in the right spot, backing up, the communication factor. Kind of the captain of the infield out there. He's just such a good pro. I just look forward to his presence back in our lineup on both sides of the ball."

Aaron Judge is also continuing to make progress as he looks to return from a fractured right wrist, sustained July 26. Boone said Judge -- who stood in against Masahiro Tanaka's bullpen session Tuesday -- performed baserunning and outfield work before hitting off a tee Wednesday.
"Another positive step forward, responded well, felt good," Boone said. "He was able to pop the ball. We'll continue with that through the weekend and get to soft-toss. He may get in the cage at some point, but he's building a little bit of momentum."
This date in Yankees history
Sept. 5, 2007: Bob Sheppard works his final game as the public-address announcer at Yankee Stadium, a 10-2 victory over the Mariners. Alex Rodriguez homered twice in an eight-run seventh inning, marking the first two-homer inning by a Yankee since Cliff Johnson on June 30, 1977, at Toronto.