Houston Texans wide receiver Andre Johnson suffered a chest contusion during Sunday's 24-21 victory over the San Francisco 49ers.
"We're concerned," Kubiak said. "He could not go at the end, and so there is concern until we see."
Johnson was shaken up on a play during the fourth quarter and remained on the field on his hands and knees for a few minutes before walking to the sideline. He returned for one play a few minutes later, but he was held out of the Texans' next series.
Johnson was seen talking to the team's medical staff for several minutes before he was escorted off the field.
Johnson finished the game with two receptions for 62 yards.
The Associated Press contributed to this report