Limited in practice throughout the week, Garcon missed last week's game against the St. Louis Rams after getting injured in the season opener against the New Orleans Saints. He had an 88-yard touchdown catch in that contest.
"Pierre is doubtful," Shanahan said. "He went through drill work, still a little sore, but he didn't take any reps in team so unless he can go before the game, we'll list him there."
Shanahan went on to say he's unsure when Garcon will return.
"He either can do it or he can't," Shanahan said. "He pushed pretty hard today. He was just a little bit too sore. He got some good work in early. But until it gets good enough to go, there's always that question mark."