Quarterback Jimmy Garoppolo could get his first start as the 49ers quarterback against the Bears on Sunday.
Garoppolo was acquired by the 49ers in a trade with the New England Patriots last month.
Garoppolo can only hope his first 49ers start goes as spectacular as he finished his 49ers debut Sunday, when he threw a touchdown pass as time expired, albeit in a 24-13 loss to the Seattle Seahawks at Levi's Stadium.
In 18 career games, Garoppolo has completed 67.7 percent of his passes for 708 yards, throwing six touchdown passes and no interceptions.
Beathard was injured in Sunday's game against the Seattle Seahawks, which pressed Garoppolo into brief duty.
Beathard started the past five games after replacing Brian Hoyer, who began the season as San Francisco's starting quarterback. In two starts with the Patriots, he threw four touchdowns, zero interceptions, and had a rating of 120.8.
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Beathard's 69.2 passer rating ranks 34th among qualified quarterbacks.
Shanahan said Monday he wanted his starting quarterback to take all the necessary reps in practice to prepare for Sunday and there questions as to Beathard's availability for Wednesday's practice.
The 49ers announced Tuesday night that Garoppolo, who is from northwest suburban Arlington Heights and played football at Rolling Meadows High School before starting three season at Eastern Illinois University, will start Sunday against the Bears.
"To give those guys the best chance to be successful, you want to give them all the reps, which still isn't enough reps", Shanahan said Monday.