Two sources say Brad Childress has given Brett Favre a deadline of this week to decide whether or not he is interested in joining the Vikings. Favre, however, is apparently reluctant to commit to playing a 19th NFL season without first being more confident the arthroscopic surgery performed recently on his throwing shoulder has succeeded in eliminating all of the problems related to a torn biceps tendon. According to sources, Favre is conflicted between his desire to provide the Vikings with the quarterback he believes is the only thing they lack to be a legitimate Super Bowl contender and his resolve to feel confident enough in his shoulder that it will not undermine his performance.