In three years at Penn State, Saquon Barkley racked up 1,195 rushing yards and eight touchdowns on 5.7 yards per carry. However, in his second series on the field, Mayfield connected with tight end David Njoku for a short touchdown pass.
Callaway, the Browns' fourth-round pick, played despite being cited for marijuana possession and driving with a suspended license. He continued marching the offense, twice keeping the drive alive with his legs - on third-and-6 and fourth-and-2 - to set up Cleveland with first-and-goal.
Mayfield returned in the third quarter to spin additional magic, rolling to his right on a third-and-7 from his own 22 to find rookie Antonio Callaway along the sideline for 24 yards.
Mayfield's National Football League debut got off to a rocky start after some conservative play-calling.
It's only one preseason game, but there were plenty of reasons to be hopeful.