Apr 09, 2009 11:47 AM EST

Concerns raised by insurance companies over Brandon Webb's arm caused the Diamondbacks to withdraw their offer of a three-year, $54 million contract extension to the right-hander last June, according to major-league sources.

Webb passed a team physical, sources say, but insurance companies use a higher standard when assessing risk. Multiple companies raised concerns, creating a "red flag" for the Diamondbacks, sources say.

Via FoxSports