ATLANTA -- There was a sound of relief in Aaron Boone's voice Monday afternoon.

"We got some answers," the New York Yankees manager said.

With the Yankees announcing Monday a six- to eight-week recovery period for first baseman Greg Bird, who's undergoing foot surgery Tuesday, the team has the certainty -- and, it hopes, the sense of finality -- that was so elusive when Bird first started feeling pained over the weekend.

The worry, for now, is behind them. The path forward without Bird looks clear. So, who's on first now?

"This time of year," general manager Brian Cashman said, "you go with what you got."

Translation: The Yankees' plan to replace Bird for the foreseeable future rests with the players currently on their roster.

Beginning Opening Day, expect some combination of 10-year veteran Neil Walker and 26-year-old Tyler Austin to play first base until Bird returns.

"I feel like I'm really prepared," Austin said. "I've gotten out and gotten early work every single day. Whether I was in Double-A in 2016, even when I got called up to Triple-A, and then last year, even when I was healthy, I was out just about every day; especially at home, getting early ground balls."

Austin has spent 51 games with the major league club the past two seasons, batting .236 with seven home runs and a .741 OPS. He has spent more than half those games playing first base.

"His strike-zone discipline is pretty good," said Boone, acknowledging that he felt Austin hit better than his average indicated. "We'll leverage some matchups that will play in his favor, and his power could come into play. I'm confident we have a chance to have a good player on the days he's in there."

Currently, Austin appears the early favorite to get the most chances to play first with Bird shelved.

"We're certainly going to miss Greg, but we feel good about what we can do from a matchup standpoint with these guys," Boone said. "We feel like Tyler Austin is ready for this opportunity. He was just blocked by Greg Bird."

But that doesn't mean anyone should count out Walker. He's very much in the mix, too.

Signed as a free agent on March 12, Walker is among the newest Yankee additions. He's also a multi-positional player, having appeared at first, second and third base for various teams throughout his career.

Walker has spent his limited time in pinstripes practicing equally at all three positions. But game action is more meaningful to him.

"Fortunately I got a few games in there and taking ground balls and a throw to second are the things that you need to get reps on, just with guys moving, with runners moving and double-play situations and all of that," Walker said. "Nothing I haven't experienced before. But it's like anything else, the more reps you get, especially game reps, the more comfortable you'll be."

Including Monday's exhibition at SunTrust Park, Walker appeared at first base in three of the seven spring games he has played with the Yankees.

Boone said Monday he's still tinkering with his starting lineup for Thursday's opener in Toronto. But with left-hander J.A. Happ on the mound for the Blue Jays, Boone is open to the possibility of having the switch-hitting Walker and the right-handed swinging Austin playing next to each other at second and first base, respectively.

Whatever the Yankees' first batting order of the season proves to be, Boone will search for Bird's replacement on a game-by-game basis.

"It depends on the matchups, honestly. Not just who we're facing, but maybe who's on the mound for us, and what kind of defense we want to have out there," Boone said. "All those things will come into play."

If for whatever reason the Yankees needed to add to the first-base depth later in the season, they also have a pair of players in the farm system who are getting work at the position. Billy McKinney, who torched through Yankees spring training with a team-leading five home runs, has spent some time this spring playing first. He also played 11 games there during the most recent Arizona Fall League.

With McKinney in Triple-A at the start of the season is Miguel Andujar, another spring power-hitting phenom who had four homers in a four-game stretch at the start of Grapefruit League action. Cashman said last week that Andujar would be getting an 80 percent/20 percent split of time practicing at third base and first base this minor league season.