A's expected to add infielder Lamb (source)

After losing two third basemen on the same day, the A’s could be reaching outside the organization for help.

The Athletics are expecting to sign veteran infielder Jake Lamb, a source confirmed to MLB.com. Since Lamb was designated for assignment by the D-backs on Friday, Oakland can’t officially sign him until Monday, when he becomes a free agent.

“I can’t comment on that because it hasn’t happened yet,” A’s manager Bob Melvin said on Sunday when asked about the possibility of adding a free agent. “I can’t go there, unfortunately.”

Lamb was an All-Star in 2017, slashing .248/.357/.487 with 30 home runs and 105 RBIs. But shoulder injuries have plagued the 29-year-old infielder in recent years, limiting him to 152 games over the past three seasons. With the deadline for postseason-eligible players to be added to the roster looming on Tuesday, Lamb would be eligible for the playoffs if he does end up signing on Monday.

The search for another third baseman comes after the club announced on Saturday that Matt Chapman would undergo season-ending surgery on his right hip. Chad Pinder, who was expected to get an uptick in playing time at the hot corner in place of Chapman, sustained a right hamstring strain in Saturday’s doubleheader and he was placed on the 10-day injured list, increasing the necessity for another infielder.

For the interim, the A’s recalled utility infielder Nate Orf from the club’s alternate training site on Sunday to take Pinder’s spot on the active roster. Orf, 30, was a non-roster invitee to Spring Training for Oakland after spending his 2019 campaign in the Brewers’ system, hitting .272 with 11 home runs and 54 RBIs over 125 games with Triple-A San Antonio.

“I loved him [in Spring Training],” Melvin said. “Versatile, scrappy player that can play any position and gives you a tough at-bat. I think he’s a nice guy to have in our [player] pool. He was the right guy.”

Pinder will undergo an MRI on Monday in Seattle, where the A’s will play a doubleheader against the Mariners. At this point, Melvin isn’t sure how long Pinder might be sidelined.

“Pinder is a guy that has been a leader with these guys all through the Minor Leagues,” Melvin said. “Pinder is the guy that keeps everybody under control. He has a great way of talking to guys and understanding what they’re going through. Hopefully, we have him around. My guess is he’ll rehab with us. He’s very impactful in our clubhouse.”

Martin Gallegos covers the A's for MLB.com. Follow him on Twitter @MartinJGallegos.