Drew Dudzik had his worst game as a James Madison quarterback in Saturday's 24-17 loss at Hofstra.
On Monday, Matthews provided a likely explanation, saying Dudzik played most of the game with a concussion.
During one exchange on the sideline, "He looked at me like he didn't know who I was," Matthews said at his weekly press conference. "So I'm not sure Drew was in the stadium."
Dudzik was 5-11 passing for just 19 yards and an interception, and ran for 11 more yards.
Said Matthews: "We should have picked up on it, but we didn't."
Dudzik also left JMU's spring game this past April with a concussion.
Matthews called the injury "a concern," but said Dudzik seemed to be fine physically at the team's workout Sunday night.
But JMU's starting running back, Jamal Sullivan, is still less than fine, Matthews said.
According to Matthews, Sullivan described himself as 75 percent healthy on Sunday night.
Sullivan missed the Hofstra loss while recovering from a bruised patella suffered in JMU's win at Liberty.
Matthews doesn't expect the junior to be ready to play Saturday, when JMU hosts No. 1 Richmond.
"I just think it's going to take two weeks, so we'll see," said Matthews. "That was a very significant bruise."