FLOWERY BRANCH, Ga. — For most N.F.L. players, their size is a dead giveaway to their position. Then there is Jacquizz Rodgers.

When the rookie offensive lineman Peter Konz first spotted Rodgers at the Atlanta Falcons’ practice complex, “I didn’t know what exactly he played,” Konz recalled Thursday. “Defensive back? Return specialist?”

Rodgers, all 5 feet 6 inches of him, is primarily a running back.

On a first down on Sunday, from deep in his own territory, the 6-foot-4 quarterback Matt Ryan leaned over — and over — and handed off to Rodgers. Rodgers burst through the line, shed a Seattle defender who had a fistful of his red jersey and came face mask to face mask with Seahawks free safety Earl Thomas.

The subsequent collision flattened Thomas but barely fazed Rodgers. The play, a 45-yard gain, “got everybody fired up,” Rodgers’s fellow tailback Michael Turner said.