NAPA, Calif. --Donald Penn, the Oakland Raiders' Pro Bowl left tackle, did not arrive for reporting day at training camp Friday and is holding out, a source confirmed to ESPN.
Penn skipped the first day as a show of frustration over his contract, according to NFL Network. Penn's deal is entering its second and final year, and he wants his salary to reflect his standing as a top-10 left tackle against the pass rush.
The Raiders had no comment, and Penn did not respond to a message.
Penn is due a base salary of $5.8 million this season, which ranks 11th among pure left tackles, according to ESPN Stats & Information.
"We've talked throughout the offseason," Pro Bowl center Rodney Hudson said Friday of Penn. "I haven't quite spoken to him today, but those things are going to work itself out at some point."
The Raiders re-signed Penn to a two-year, $11.9 million contract in March 2016, and he gave up only one sack on 621 pass snaps last season, according to Pro Football Focus, though it was a costly one. Penn was blocking then-Indianapolis Colts linebacker Trent Cole in Week 16 when Penn slipped and Cole sacked quarterbackDerek Carr, who suffered a season-ending broken right fibula on the play.
A week later, in the season finale, Penn suffered a left knee injury that kept him out of the Raiders' playoff loss at Houston. Menelik Watson started the game at left tackle and departed in free agency for the Denver Broncos.
Penn, whose current contract carries a salary-cap number of $7.15 million, has never missed a regular-season game since entering the NFL as an undrafted free agent out of Utah State with the Tampa Bay Buccaneers in 2007. PFF has ranked him among the top-12 tackles each of the past three seasons, and his blocking scores have improved each year since 2014.
During organized team activities, Penn was asked about preparing to play as a 34-year-old veteran.
"You have to listen to your body," he said. "You have to rest when it's time to rest. When you have a day off during camp, if I don't have to do anything, I'm not going to do anything. I'm going to sit on the couch and get a massage, get in the ice tub, I'm going to relax. You have to rest when it's time to rest and be smart about stuff.
"That's the type of guy I am. I don't want to be out. I feel good. I don't feel 34. I don't at all."
Earlier in the day, Austin Howard, who started 39 games for the Raiders in three years, including 10 last season at right tackle, posted on Instagram that his days with the team were finished, and the team released him.
The Raiders have also yet to sign first-round draft pick Gareon Conley. The Raiders' first training camp practice is Saturday.