Durham, 34, in the last year of his three-year contract, had hoped to stay off the disabled list this season -- as he did in 2005 despite leg problems -- but incurred an irritation to his left hamstring tendon last Sunday in Colorado as he ran hard toward first on an infield grounder.
"He didn't respond the way we thought he was going to," Giants head trainer Stan Conte said. "We gave him an injection that didn't make a difference. He came in [Thursday] and he couldn't do anything comfortably. We decided to give him some healing time."
The veteran was hitting only .203 with one homer and eight RBIs this year.
"It's going to be awhile before he's ready," Giants manager Felipe Alou said. "So we'll give him the two weeks. He'd only be able to pinch-hit and he's an everyday guy."
Frandsen, only 23, played at Class A San Jose, Double-A Connecticut and Triple-A Fresno last season, wowing coaches and observers with classy fielding, good speed and an excellent hitting eye.
This spring, Frandsen sparkled, batting .358 over 30 games with six doubles, two triples, two homers and 12 RBIs while finishing second on the club with 14 runs scored. He also boasted a .597 slugging percentage.
"I played that guy every day we had a game in Spring Training," Alou said. "We have confidence in him."
With the Grizzlies this season, the San Jose, Calif., native was hitting .333 and leading the Pacific Coast League with 11 doubles.
"He hasn't had a lot of Minor Legue experience or at-bats," said Sabean, "but he seems to be a natural. He adds a lot of depth on an everyday basis."
Frandsen, who can also play third base, had a .328 career mark on farm clubs entering this season and was named the Giants' fifth-best prospect by Baseball America
following the 2005 campaign.
To make room for Frandsen on the 40-man roster, the Giants transferred Minor League right-hander Kelyn Acosta, who is recovering from right elbow neuritis, from the 15-day DL to the 60-day DL.