Hairston said that he's had pain in his elbow for the past six weeks but has been able to play through it. Only in the last few days did the pain get to the point where it was very painful to throw.
Hairston has been told that he won't need surgery but that the ligament will need two to three weeks for a complete recovery.
Manager Bud Black said after the Padres' 3-2 loss to the Phillies on Friday that Hairston will be placed on the disabled list on Saturday with a corresponding move to be announced.
Hairston -- who has started 102 games this season among shortstop, second base, third base, left field and right field -- said the elbow doesn't hurt to hit. He served as a pinch-runner and scored the tying run in the ninth inning on Friday.
"It's progressively gotten worse ... I've tried to fight through it," Hairston said before Friday's game. "We'll just rest it and it will get better. They're debating on whether to keep me active or not."
Hairston is hitting .249 this season and has also tied his career high with 10 home runs. He has 50 RBIs, though his true value can be measured on defense, where he stepped in and replaced Everth Cabrera at shortstop during two disabled-list stints.
In addition to starting 53 games at shortstop, Hairston has made 42 starts at second base, many when David Eckstein missed 29 games in July and August with a right calf strain.
Hairston, who has also been battling shin splints in recent weeks, doesn't like the idea of coming out of the lineup.
"I'm one of those guys from the Cal Ripken school, and I played with Cal," Hairston said of his time with the Orioles at the twilight of Ripken's career. "The last six weeks have been tough."
The return of Eckstein from the disabled list and the addition of Miguel Tejada before the July 31 non-waiver Trade Deadline has allowed Black to use Hairston -- who signed a one-year deal as a free agent before the season -- to be used as the team originally intended, as a utility man.
The Padres could recall Cabrera, who was optioned to Triple-A Portland on Aug. 21 but could return with Hairston going to DL.
The Padres could reinstate infielder Oscar Salazar from the disabled list Saturday. Salazar was hitting .285 in seven games while on a Minor League rehabilitation stint with Class A Lake Elsinore.
Salazar has missed 27 consecutive games with a strained right Achilles tendon.