Thanks to Mariano Rivera, the Yankees have had a unique advantage over everyone else for nearly two decades because of their bullpen's ability to shorten games. Following his retirement, that luxury may be gone.

All eyes will be on David Robertson, who will try to fill the shoes of baseball's all-time saves leader. Even though it is a tall task, when Rivera tore his ACL in 2012, Rafael Soriano filled in admirably with 42 saves and a 2.26 ERA.

While Robertson has been an excellent set-up man, earning an MLB-best 97 holds over the past three seasons, he has yet to prove his ability to close games. Although many seem to believe that pitching the ninth inning is another animal,Robertson shouldn't have much trouble transitioning, even though he isn't replacing any run-of-the-mill closer.

The real issue is who replaces Robertson as the set-up man. It's expected that the Yankees will feature Shawn Kelley in the eighth inning. The 29-year-old averaged a career-high 12 strikeouts per nine innings last season in his first year with the Yanks, although his 4.39 ERA was less than flattering.

Another concern is the lefty arm in the pen. Effective lefty-specialist Boone Logan hiked to the Rockies after agreeing to a 3-year, $16.5 million deal in the offseason. The Bombers are replacing him with 37-year-old Matt Thornton, who allowed lefties to hit only .235 against him in 2013. Unlike Logan, however, Thornton was lit up by righties, who hit .333 against him last season.

In addition to long men Adam Warren, Vidal Nuno and David Phelps, Preston Claiborne and Dellin Betances round out the bullpen.. There are some question marks and they may take a small step backwards minus Rivera, but if Robertson is successful, the pieces will fall into place.