NAPA, Calif. -- Trent Richardson is finally starting his quest to reclaim a once-promising NFL career.

The former Alabama star running back practiced Thursday with the Oakland Raiders for the first time this training camp after missing the first five days of camp practice while on the non-football illness list.

Richardson on Thursday said he was battling pneumonia for a couple of weeks before the start of camp but is feeling well now.

Oakland coach Jack Del Rio had said Richardson worked himself down to the 220-pound range. He was reportedly weighing in the 240s last season in Indianapolis.

Trent Richardson practiced Thursday after missing the first five days of Raiders camp. AP Photo/Eric Risberg

"I really believe with him committing himself like that and getting himself in that kind of shape, he'll have a chance to come out here and show what he's really capable of," Del Rio said of Richardson on Sunday night.

The Raiders surprised many in the league by giving the 25-year-old Richardson $600,000 in guaranteed money even though he's averaging 3.3 yards per carry in his career. He was the No. 3 overall pick by Cleveland in the 2012 draft.

The Browns traded him to Indianapolis in 2013 for a first-round pick. He was cut by the Colts this offseason.

Richardson was expected to be the backup to Latavius Murray this season, but undrafted rookie Michael Dyer has put pressure on Richardson by having a strong first week. Dyer missed his first practice of training camp Thursday for an undisclosed reason.