Gore said Saturday in an interview with TheSFNiners.com that he plans to sign a one-day contract with the 49ers soon to formally announce his retirement from the NFL.

Gore has yet to formally announce his retirement from the NFL, but the 38-year-old told Ian Rapoport of NFL Network that he's been training for both football and boxing.

Gore (lung contusion) said Tuesday that he hasn't determined whether he wants to return to the NFL for a 17th season, Eric Allen of the Jets' official site reports. "I still have fun playing the game of football, but I haven't made a decision yet," Gore said of his future.

Gore (chest) was placed on IR on Wednesday, Andy Vasquez of USA Today Sports reports.

Gore is dealing with a lung contusion and has been ruled out for the Week 17 game against the Patriots, Al Iannazzone of Newsday reports.

Gore suffered a chest injury in the second half of Sunday's 23-16 win over the Browns, Connor Hughes of The Athletic reports. He rushed 14 times for 48 yards and caught his only target for five yards prior to sustaining the injury.

Gore carried the ball 23 times for 59 yards and a touchdown in and caught his only target for six yards in Sunday's 23-20 upset of the Rams.

Gore carried the ball eight times for 23 yards and caught his only target for eight yards in Sunday's 40-3 loss to the Seahawks.

Gore (concussion) is listed as active for Sunday's game against the Seahawks.

Ian Rapoport of NFL Network indicates that "there is optimism" that Gore (concussion) will play Sunday against the Seahawks.