New 49ers running back Reggie Bush will wear No. 23 this season. It's unlikely he asked for No. 21, which he wore for two seasons in Detroit, but it would have been unavailable if he had considering it once belonged to the team's all-time leading rusher, Frank Gore.

That jersey and 15 others are off limits to the 90 players who will be taking part in the 49ers' offseason, which means, as usual, a few players will double up on jersey numbers this spring and summer.

The 49ers have officially retired 12 jerseys, including hall of famer Bob St. Clair's No. 79. St. Clair passed away on Monday.

No one has worn Bryant Young's No. 97 since Young retired after the 2007 season. Gore's No. 21 and Patrick Willis' No. 52 are unlikely to be worn in coming seasons. Thomas Herrion, who died of a heart condition shortly after a preseason game in Denver in 2005, wore No. 72, which also hasn't been used since.

That means Glenn Dorsey won't be wearing the jersey number he wore at LSU and with the Chiefs. Dorsey, who has worn No. 90 for the 49ers, recently have that number to fellow defensive lineman Darnell Dockett.

Other number selections for incoming players, according to the 49ers:

WR Jerome Simpson, No. 14

CB Shareece Wright, No. 29

RB Jarryd Hayne, No. 38

LB Nick Bellore, No. 50

LB Desmond Bishop, No. 51

OL Erik Pears, No. 71

WR Torrey Smith, No. 82

The NFL in March voted to allow linebackers to use numbers in the 40s. Last decade, the league began allowing receivers to wear numbers in the teens. The last player to wear No. 00 was Kenny Burroughs for the Houston Oilers.

Retired numbers

8 -- QB Steve Young

12 -- QB John Brodie

16 -- QB Joe Montana

34 -- RB Joe Perry

37 -- DB Jimmy Johnson

39 -- RB Hugh McElhenny

42 -- S Ronnie Lott

70 -- DT Charlie Krueger

73 -- T Leo Nomellini

79 -- T Bob St. Clair

80 -- WR Jerry Rice

87 -- WR Dwight Clark