Gannon's shoulder still ailing after Raiders QB hurt Monday night
ALAMEDA, Calif. -- Rich Gannon underwent tests on his injured shoulder Tuesday, and Oakland Raiders coach Bill Callahan would not guarantee the quarterback's starting job until the results were known.
Gannon, a four-time Pro Bowler and last season's league MVP, was pounded by the Kansas City defense throughout the first half of the Raiders' 17-10 loss to the Chiefs on Monday night.
He was held out of the second half with a bruised right shoulder. Seldom-used backup Marques Tuiasosopo led Oakland on a fourth-quarter rally, nearly tying the game in the final seconds.
Callahan praised both Gannon and Tuiasosopo on Tuesday, but said he isn't sure who will be the Raiders' first-stringer when the team returns from its bye week. The Raiders are expected to find out the severity of Gannon's injury on Wednesday.
"I'm not going to make any determination on the quarterback's play until I know about his health situation," Callahan said of Gannon. "This is the league's MVP. I have great respect for him and everything he has done for the team."
After he was sacked by linebacker Shawn Barber on the final play of the first half, Gannon went to the sideline holding his arm. Gannon, 10-of-19 for 58 yards and an interception, received treatment on the sideline while Tuiasosopo played the second half.
"When I tried to throw, I couldn't," Gannon said Monday night.
Tuiasosopo, a seldom-used backup who had just 69 yards passing in his career, rallied the Raiders to three lengthy drives and 10 points in the fourth quarter. But the comeback attempt ended when two Chiefs tackled Tim Brown at the Kansas City 1 as time expired.
Earlier in the season, Callahan dismissed any notion of occasionally using Tuiasosopo to keep Gannon fresh. But when asked directly Tuesday whether Gannon's job was safe if the MVP's health was sound, Callahan said: "I'm not going to make that decision or even speculate or go there at this point."
Oakland's players had the day off Tuesday.
While leading the Raiders to three straight AFC West titles, Gannon has been the focal point on one of the league's most consistently excellent offenses. Last season, he led the NFL with 4,689 yards passing while setting league records with 418 completions and 10 300-yard passing games.
But the 37-year-old quarterback has been mostly terrible this season along with his teammates as Oakland stumbled to a 2-5 start. With a dismal passer rating of 73.5, Gannon has thrown for just 1,274 yards with six touchdowns and four interceptions.
This story is from ESPN.com's automated news wire. Wire index