The Washington Post’s LaVar Arrington describes the complex coach-player relationship in the NFL and how that dynamic played a key role in Mike Shanahan’s decision not to bench Robert Griffin III in the Redskins’ loss to Seattle on Sunday. (The Washington Post)

The NFL Players Association is expected to decide soon, perhaps Friday, whether to demand a formal investigation of the Washington Redskins’ handling of the knee injury suffered by quarterback Robert Griffin III under the sport’s collective bargaining agreement, a person familiar with the situation said Thursday.

The union also issued a public plea Thursday for the Redskins to improve the quality of the playing surface at FedEx Field.

Griffin, the Redskins’ brilliant 22-year-old rookie quarterback, is recovering in Florida after undergoing surgery there Wednesday on two torn ligaments in his right knee. His season ended when he left Sunday’s playoff loss to the Seattle Seahawks after re-injuring his knee. He was playing in his third game since he suffered a mild sprain of the lateral collateral ligament in that knee.

“Our medical director, Dr. Thom Mayer, has been in contact with the Redskins and has asked for a report on Robert Griffin III’s medical diagnosis and treatment,” George Atallah, the union’s assistant executive director of external affairs, said by telephone Thursday.

Under the CBA, the league and union have a joint committee on player safety and welfare. The CBA gives the union the right “to commence an investigation before the joint committee if the NFLPA believes that the medical care of a team is not adequately taking care of player safety.”

The Post’s LaVar Arrington wonders if Robert Griffin III will ever be the same quarterback after suffering another knee injury in the Redskins’ loss to the Seahawks and offers his injured pinky as a small example of this type of damage that a body can absorb during a career in football. (The Washington Post)

Also Thursday, Mark Adickes, the former Redskins lineman turned orthopedic surgeon who performed reconstructive surgery on Griffin’s right knee in 2009, predicted that Griffin could return from his latest surgery in time for the Redskins’ 2013 regular season opener. He also said the quarterback would make a full return to his 2012 pre-injury level of play.

“I would think eight months would be the number,” Adickes said when asked to estimate when Griffin might return to action. A timetable of eight months would put Griffin’s return in early September 2013, about the time the Redskins open the season.

Asked about a potential return to Griffin’s pre-injury ability, Adickes said, “I think his knee is going to be rock solid and he’ll be able to be the guy we saw this year.”

Other sports orthopedists not involved in Griffin’s care and with no specific knowledge of Wednesday’s surgery have estimated Griffin’s return at eight to 12 months. Several physicians have suggested Griffin may not be able to make a complete return to his previous level of speed, agility and explosiveness.

Adickes, who is based in Houston, was not involved in Griffin’s latest surgery, but has consulted with Redskins medical personnel and has been in close contact with Griffin’s family.

He revealed two additional aspects of Griffin’s surgery that the Redskins did not address in the statement they released from orthopedic surgeon James Andrews, who repaired Griffin’s lateral collateral ligament and reconstructed his anterior cruciate ligament Wednesday. That statement is the only formal announcement about Griffin by anyone associated with the team.

According to Adickes, Griffin also suffered a slight tear of his medial meniscus, which Andrews was able to repair. In addition, in order to reconstruct the torn ACL, Andrews took a portion of bone and tendon from Griffin’s left (healthy) knee and grafted it to his right knee, a fairly common procedure for a revision of an ACL reconstruction.

Adickes said Griffin may have some discomfort in his left knee and will have more trouble getting around on crutches because of the left knee surgery. But neither the meniscus tear nor the left knee graft will lengthen Griffin’s recovery time, Adickes said.

If the NFLPA initiates a formal inquiry, two or more independent physicians would be chosen to conduct an investigation and issue a report. The CBA says that “their recommendations as to what steps shall be taken to address and correct any issues shall be acted upon by the Joint Committee.”

According to a person with knowledge of the situation, the union’s focus is whether the Redskins followed the recommendations of their medical staff about when to play Griffin. The union’s probe does not focus on coaching decisions made by Coach Mike Shanahan, other than the issue of whether he followed the recommendations of doctors, the person said.

According to that person, the union has sought information going back to the Dec. 9 game against the Baltimore Ravens, when Griffin originally suffered his LCL sprain on a hit by Haloti Ngata.

Shanahan has said he followed the recommendations of doctors.

Andrews, who is on the sideline for Redskins games, told USA Today last weekend that he did not clear Griffin to return temporarily to the Ravens game, in contrast to Shanahan’s version of events. But Andrews later told The Washington Post that there was “a communication problem” between him and Shanahan.

Andrews said he didn’t get a chance to examine Griffin but gave Shanahan a hand signal to indicate that “I guess he’s okay” to play. Griffin, after missing one play, returned to that game for four plays before leaving for good.

Griffin remained in Sunday’s loss to the Seahawks after appearing to re-injure his knee on a first-quarter play. Griffin and Shanahan said later that the quarterback urged Shanahan to leave him in the game, and Shanahan agreed.

DeMaurice Smith, the union’s executive director, told ESPN earlier this week that the union had initiated formal investigations of teams’ handling of injuries on “at least three occasions” under the CBA, which was completed in 2011. Smith said in that televised interview that the union was looking into Griffin’s injury because “there was enough of an inconsistency or a question about whether the process of evaluating the player occurred, whether he was cleared to play, not cleared to play.”

Of the condition of the field, Atallah said Thursday: “The coaching staff and players for both teams have spoken out against the quality of the field during Sunday’s game. We would hope that significant improvements would be made.”

Seahawks Coach Pete Carroll was highly critical Monday of the condition of the field during Sunday’s game. It is unclear if the condition of the field contributed to Griffin’s injury. Shanahan said Monday he might be receptive to the possibility of a switch to an artificial playing surface at Fed­Ex Field.