Jim Trotter thinks the NFL should have acted faster on removing controversial medical adviser Elliot Pellman from his position with the league. (1:16)

The NFL will replace longtime and controversial medical adviser Elliot Pellman with a new full-time chief medical officer, commissioner Roger Goodell wrote Wednesday in a letter to club executives.

Pellman will retire, Goodell wrote, but the commissioner made the decision that prompted Pellman's retirement, sources told ESPN's Adam Schefter. Goodell understands that the NFL must demonstrate strong leadership on health and safety and that its players and fans need to trust in the league, the sources said.

Pellman is retiring after a 30-year career with the NFL. A rheumatologist, Pellman had served as New York Jets team doctor and was also chairman of the league's powerful research arm.

Pellman has been a central figure in the NFL's attempts to deal with rising concerns about concussions. For more than two decades, Pellman presided over the NFL's Mild Traumatic Brain Injury committee -- a group consisting largely of NFL trainers and doctors. The MTBI committee, formed in 1994 by then-commissioner Paul Tagliabue, spent decades producing studies that portrayed concussions as minor injuries, while Pellman and his colleagues attacked independent scientists who linked football to brain damage.

Elliot Pellman, who has been a central figure in the NFL's attempts to deal with rising concerns about concussions, is retiring at the suggestion of commissioner Roger Goodell. AP Photo/Gerald Herbert

In a 2013 story, Outside the Lines revealed that Pellman had served for years as Tagliabue's personal physician. An earlier ESPN piece described how Pellman used the questionable conclusions of the MTBI committee in his work with the Jets, often allowing concussed players back into games. In 2005, the New York Times revealed that Pellman embellished his credentials and failed to disclose that he attended medical school in Guadalajara, Mexico. Pellman resigned as chairman not long after, though he remained on the committee.

In 2010, under pressure from Congress, commissioner Roger Goodell disbanded the MTBI committee and replaced it with the Head, Neck and Spine Committee. The new leaders of that group agreed with assertions that the MTBI Committee's work was "infected" and said they would use none of the previous studies.

Pellman was removed from the committee, but, to the surprise of many researchers, he maintained a role a medical advisor within the league offices.

On Wednesday, Goodell wrote that the new chief medical officer's role will be to coordinate health-related efforts with team medical staffs, the NFLPA and medical committees. The new hire will ensure that teams have access to updated information and that NFL research funds are spent "in an effective and targeted way," according to Goodell.

In May, a congressional report concluded that the NFL had pressured the National Institutes of Health to strip the $16 million project from a prominent Boston University researcher. It also determined the NFL tried to redirect the money to members of the league's committee on brain injuries. The study was to have been funded out of a $30 million "unrestricted gift" the NFL gave the NIH in 2012.

A search for the NFL's new full-time chief medical officer role will begin this week and will be conducted by a panel of health and medical experts led by Dr. Betsy Nabel, the league's chief health and medical adviser.

Others on the search panel will include Dr. Rob Heyer, president of the NFL Physicians Society and team internist for the Carolina Panthers; Ronnie Barnes, senior vice president and head trainer for the New York Giants; Dr. Robert Cantu of Boston University; and Peter Foss, of G.E. Healthcare. The panel will work closely with the league's Jeff Miller.

Steve Fainaru and Mark Fainaru-Wada and The Associated Press contributed to this report.