While Boston’s negotiations with C Jason Varitek continue, ‘Tek’s capable back-up, Doug Mirabelli, is expected to sign an extension with the club shortly writes the Boston Globe’s Bob Hohler.

Mirabelli, a free agent for the first time, appeared poised to nearly double his salary from the $825,000 he earned last season. While serving primarily as Tim Wakefield’s personal catcher, Mirabelli set career highs in batting average (.281), runs (27), RBIs (32), on-base percentage (.368), and slugging percentage (.525).

The Sox reached the tentative accord while a number of teams eyed Mirabelli as a prospective backup amid significant movement in the catching ranks. In recent days, the Brewers signed Oakland free agent Damian Miller, the Twins picked up Florida free agent Mike Redmond, the Angels exercised Bengie Molina’s option, and the A’s were close to acquiring Jason Kendall from the Pirates for lefthanders Mark Redman and Arthur Rhodes.

Though the Sox placed a high priority on retaining Mirabelli, they have no plans to significantly expand his backup role and remain committed to pursuing Varitek, the top catcher on the free agent market. The Sox have offered Varitek about $36 million over four years while he has sought $55 million over five years, and the sides may need a while to resolve their differences. (With the Sox expected to offer Varitek salary arbitration by Dec. 7, he would have until Dec. 19 to decide whether to accept. If he were to reject the offer, the sides would have until Jan. 8 to reach a deal or forfeit their rights to negotiate until May 1.)