Updated

The simmering feud between Donovan McNabb and Mike Shanahan and his son continued Thursday with a blistering statement from the quarterback's agent.

Fletcher Smith took aim directly at the Washington coach and Kyle Shanahan, the Redskins' offensive coordinator, for the way they have handled the benching of his client.

Smith said the bad blood between the quarterback and the Washington coaches is due to McNabb's suggestions for improving the Redskins' offense.

"I believe there is tension between Donovan and Kyle that's rooted in the fact that Donovan has suggested modifications to Kyle's offense based on intricacies Donovan has learned in his NFL career," Smith wrote. "For example, Donovan has asked all year that the team run more screen passes to help manage the pass rush more effectively. Ironically, Kyle decided to employ Donovan's suggestions after he unceremoniously benched him on Sunday."

McNabb listened to questions from reporters Thursday while sitting in his car after practice, but did not answer before driving off. He was benched before last Sunday's game against Dallas and told by Mike Shanahan that he would not play the remainder of the season.

Smith said in a statement that the Shanahans have made comments that go beyond disrespectful and "unprecedented for a six-time Pro Bowl quarterback such as Donovan."

Smith said that the comments made by the Shanahans — "both Mike and more specifically Kyle" — have made the quarterback's relationship with Washington difficult to maintain.

Late Thursday, Mike Shanahan responded with a statement of his own.

"As I stated earlier, when I traded for Donovan McNabb I had hoped that he would lead us to the playoffs," Mike Shanahan said. "No one wanted him to be more successful than me. When the team was 5-8 and mathematically out of the playoffs, I made the decision to evaluate our other two quarterbacks.

"This was not personal, but strictly professional. The decision was made in the best interest of the Washington Redskins and I stand by my decision. I will attempt to talk to Fletcher Smith directly to clear up every one of his misconceptions."

According to Smith, Kyle Shanahan said that McNabb "will never take another snap for me again" after McNabb drove the Redskins down the field for the potential game-tying drive against Tampa Bay on Dec. 12.

The 34-year-old McNabb was listed as the No. 2 quarterback during the Redskins' 33-30 loss to Dallas. McNabb said he felt "disrespected" by the way he was benched and demoted.

"Everything was handled awkwardly," he said Tuesday on his weekly radio show on ESPN980, "somewhat to a disrespect to me and to the team."

McNabb was benched only once in 11 years with Philadelphia, and he's already doubled that total with the Redskins since being acquired by the team in April.

Shanahan yanked McNabb for Rex Grossman in the final two minutes against Detroit in October with the game on the line, then offered several strange excuses for the decision.

Smith said the benching of his client has been part of what he described as a "difficult season" for McNabb.

"Donovan is coming off a Pro Bowl season in 2009 where he threw for 3,500 (plus) yards on 60 (percent) completions, with a TD:INT ratio of more than 2:1," Smith wrote. "He also led his team to the playoffs with an 11-5 record, and that's what he hoped to accomplish in Washington.

"This year, Donovan was on pace to set the Redskins all-time passing yards mark before being benched."

Earlier this season Mike Shanahan said he felt Grossman had a better grasp of the team's two-minute offense, then said McNabb lacked the "cardiovascular endurance" to run a fast-paced drill because of nagging hamstring injuries. Kyle Shanahan said McNabb had been tipped off in advance that the team might go with Grossman; McNabb said he hadn't.

Then the Redskins gave a McNabb a five-year contract extension worth up to $78 million — though the quarterback is only guaranteed to receive an extra $3.5 million this season. The deal contains a clause that allows the Redskins to cut McNabb before next season with no further financial obligation.

McNabb has expressed a desire to return to Washington next season, and Shanahan said he would be willing to have McNabb as a backup — a pairing that seems unlikely.

Smith left the door open in his statement, saying McNabb has taken the high road during the circus-like atmosphere.

"Donovan has maintained a high level of professionalism on and off the field," Smith said. "He is determined to continue his relentless commitment to win and looks forward to the opportunity wherever that may be."