Running back Trent Richardson's comeback attempt is, for now, stuck on the runway.
Richardson suffered a hamstring injury running sprints last week during football school, according to Head Coach John Harbaugh. He was still in street clothes for Thursday's Organized Team Activity (OTA) practice.
He was one of several players who were held out because of injuries, joining injury-plagued wide receiver Michael Campanaro (calf) and rookie draft picks Bronson Kaufusi and Kenneth Dixon.
Richardson in under the spotlight this summer after he was out of football entirely in 2015.
After signing a two-year deal with Oakland last offseason, Richardson reportedly arrived at Raiders camp a little overweight. He then missed time because of pneumonia and, after notching just 42 yards on 15 preseason carries, the Oakland Raiders released him in their first round of cuts.
Head Coach John Harbaugh suggested that Richardson needs to get in better shape to prevent injuries.
"Trent just needs to get healthy," Harbaugh said. "I think the workload and the amount of work it takes to be a world-class conditioned athlete is something that he's working on right now. That's something he needs to understand and that's where he needs to get himself. When he gets himself there, he's got talent. I'm very certain he'll get there, and when he does, we'll be able to evaluate him."
The Ravens signed Richardson on April 18 after he proved he could lower his weight. The former 2012 No. 3-overall draft pick was visibly trimmed down since beginning his offseason training regimen, but that doesn't mean he's in football shape.
Kaufusi, the Ravens' third-round pick out of BYU, hasn't practiced since the beginning of rookie minicamp. The 6-foot-6 defensive end injured his back during his first field action.
Dixon, a fourth-round pick out of Louisiana Tech, tweaked his hamstring during rookie minicamp and is also still on the mend. Dixon is part of a highly competitive running back competition.
Campanaro continues to struggle with injuries, a problem that has hidden the local product's talent over the past two years. He missed seven regular-season games during his rookie season because of a hamstring injury, then was placed on injured reserve after four weeks last year.
Harbaugh said Campanaro tweaked his calf a couple weeks ago.
"I've never seen a guy work as hard as this guy has worked the last year-and-a-half," Harbaugh said. "There will be a time when he will get past this stuff and this stuff will stop happening. Hopefully it's training camp. … He was in phenomenal shape and we still expect really good things from him."
The Ravens welcomed back several players who finished last year on injured reserve, including tight end Crockett Gillmore (shoulder), center Jeremy Zuttah (pectoral), wide receiver Breshad Perriman (knee), safety Matt Elam (biceps) and tight end Dennis Pitta (hip).
Quarterback Joe Flacco (knee) watched practice in a T-shirt from the field and Harbaugh said outside linebacker Terrell Suggs (Achilles) is working out at the Under Armour Performance Center.
Inside linebacker C.J. Mosley was missing from practice for a personal reason, but has been present at other OTA practices.