ATLANTA — The Vikings traded for Joshua Dobbs on Tuesday, and prepared to make him their backup quarterback on Sunday against the Falcons.

By the end of the first quarter, he was their only QB.

After Jaren Hall led the Vikings on a 74-yard drive highlighted by a 47-yard completion to Alexander Mattison, the rookie QB sustained a concussion while trying to run for the end zone on a third down and absorbing a hard hit from Falcons cornerback Jeff Okudah before linebacker Nate Landman landed on him. Right tackle Brian O’Neill immediately waved for the Vikings’ medical staff when Hall went down, and the Vikings quickly ruled Hall out after a brief examination.

Hall finished 5 of 6 for 78 yards, while running twice for 11 yards. Dobbs threw for 1,569 yards, eight touchdowns and five interceptions in eight starts with the Cardinals before the trade to Minnesota.

In his first drive for the Vikings, Dobbs was sacked in the end zone on third down for a safety. On his second, he was sacked and fumbled at the Minnesota 26. The Falcons recovered and eventually kicked a field goal to take a 11-3 lead.