For a team that lost 93 games last season, the Red Sox will have an unusual lack of competition for roster spots once mandatory spring training workouts begin on Tuesday. Shortstop? The job belongs to Stephen Drew. First base? Mike Napoli will play as much as his balky hips allow. The starting rotation? Sorry, no openings there. And as a small group of pitchers wrapped up another voluntary session of long toss yesterday, general manager Ben Cherington all but said ready-for-the-majors catcher Ryan Lavarnway can look for apartments in Pawtucket unless the Red Sox find a taker for Jarrod Saltalamacchia over the next two months. Indeed, the real fights for jobs will take place down the road in the Minnesota Twins’ camp, even though they dropped only three more games than the Red Sox in 2012. Cherington already has given the roster an extreme makeover by using the money saved in last August’s blockbuster with the Los Angeles Dodgers to sign seven free agents and by trading for closer Joel Hanrahan. And now, with the exception of a few opportunities still available at the end of the bench, manager John Farrell’s challenge will be to fit together the new pieces, not to choose them.