Gresham underwent back surgery in July, shortly before inking a one-year deal with Arizona. Gresham had played his entire career with the Bengals, recording 62 catches for 460 yards and five touchdowns in 2014.
Charles has nine receptions for 109 yards during his three-year career.
Gresham underwent back surgery in July. If he is not ready to play by the start of the regular season, he will lose six games.
Gresham had spent his first five NFL seasons with Cincinnati, twice earning a Pro Bowl spot and averaging 56 catches for 544 yards.
Pitta has been limited to just seven games over the last two seasons after twice dislocating his hip.
His contract guarantees him $4 million this year, so the Ravens are hoping that rest and rehab will allow him to return to health and help them at some point during the regular season.
The free agent spent his first five seasons with Cincinnati and has averaged 56 catches a year. He snagged 62 for 460 yards and five touchdowns in 2014.
He is expected to begin training camp and the regular season on the physically unable to perform list, sources said. If he begins the season on the PUP list, then he will miss at least the first six games.
Pitta has yet to be medically cleared to practice. He is able to do some route running and individual drills, but he wasn't alowed to fully participate in offseason practices.
"A couple of things are going to have to happen for him to play ultimately," coach John Harbaugh said during minicamp in June. "No. 1, he has to be cleared by the doctors. And, No. 2, he has to decide if he wants to play because obviously there will be some risk involved. He hasn't been cleared by the doctors.
"As you've seen before, he's been doing the individual part of practice. Minicamp, unless you're cleared, you can't come out to practice. I don't know if that's a rule or our policy, but that's the way it goes. Until he gets cleared by the docs, he won't be able to practice and we'll just have to see where that goes from here."
Quarless was charged with a misdemeanor after firing two shots into the air outside a parking garage in Miami Beach, per police reports. He was seen arguing with two women before the incident.
Quarless was involved in a fight at South Beach and fired the gun into the ground.