Davis was on his way to play for his new club Watford against Watford when the accident happened on the M40.
Watford called their game today off as a mark of respect, and at the County Ground as the news filtered through the chants of "There's only one Jimmy Davis" could be heard.
Manchester United boss Sir Alex Ferguson said: "We are all really sad. It's terrible news.
"You could not meet a nicer and more bubbly character than Jimmy Davis.
"He was a player with real potential, that's why we sent him to Watford this season.
"We send our sincere condolences to his family and many friends. He will be sadly missed."