San Francisco 49ers running back Christian McCaffrey practiced on Monday for the first time since September, opening a 21-day window to add the reigning NFL Offensive Player of the Year to the active roster.

Head coach Kyle Shanahan said before the 49ers began their bye schedule last week the 49ers planned to have McCaffrey practice and could activate him for Week 10 at Tampa Bay.

The 49ers officially opened the practice window for McCaffrey and offensive lineman Jon Feliciano, who has been on injured reserve since the start of the season with a knee injury.

McCaffrey was idle at the start of training camp, did not participate in preseason and limited in practices before the first game of the regular season against the Jets due to Achilles soreness. He was surprisingly inactive Week 1, with the 49ers leaning on Jordan Mason as his primary replacement.

Discussing the topic of players returning to the field after injuries earlier this year, Shanahan said McCaffrey’s approach is the reason he likely won’t need much of a practice ramp up to be ready for game action.

“He’s obsessed with it,” Shanahan said, joking McCaffrey would be thinking about running routes while walking down the aisle at his own wedding.

“And so when you do get in these situations where you do get hurt and you can’t go do all that stuff, at least he’s put the work in before. So that stuff does come back fast. But he understands what it takes to play in this game, especially at the level he does. And not many people play at that level unless they are like that.”

McCaffrey led the NFL with 2,023 yards from scrimmage last season; a league-leading 1,459 rushing yards and 14 touchdowns with 67 catches for 564 yards and seven touchdowns. He had another 59 carries for 268 yards and four touchdowns plus a team-high 19 receptions for 152 yards in the playoffs.

McCaffrey last played in a game on February 11, the 49ers’ loss to the Chiefs in the Super Bowl. McCaffrey had 22 caries for 80 yards and eight receptions for 80 yards and a touchdown.