The bullpen door swung open during the Yankees' last series of the regular season and in what figures to be a sign of things to come it was David Robertson -- and not Mariano Rivera -- answering the call for a save situation.

The crowd on hand for the contest against the Astros in Houston booed and Robertson heard it. He understood that the reaction was not personal but the fans were unaware that Rivera had already decided to end his career with his emotional Yankee Stadium exit.

"I knew immediately they weren't booing me; they were booing because Mo wasn't coming into the game" Robertson said then. "They weren't happy seeing me come into the game. It's OK with me. I guess it's just part of the gig."

It is a job that barring a major signing this winter appears to be Robertson's in 2014. Baseball people have said for years that it will be an unenviable position to be the Yankees closer after Rivera just as it will be a challenge for whoever follows Derek Jeter as the everyday shortstop.

Robertson has earned a crack at those duties by proving himself as an elite setup man. Already owning an All-Star Game appearance to his name he was 5-1 with a 2.04 ERA in 70 appearances this year finishing nine games and striking out 77 in 66 1/3 innings.

"I think he's a guy that has the ability to [close]" Yankees manager Joe Girardi said. "Right now that's our best candidate."

But Robertson's best work to date has come in the eighth inning and the ninth is something of a question mark. Just 8-for-18 in save opportunities over his career Robertson was unconvincing in a brief closing cameo after Rivera's injury in May 2012 making four appearances and blowing a save before he went on the disabled list with an oblique strain.

By the time Robertson returned from the DL Rafael Soriano was flourishing on his way to a 42-save campaign as the Yanks' replacement closer so Robertson returned to his eighth-inning duties.

"The first couple times I tried it it was different because Mo wasn't coming back" Robertson said. "There was no way he could pitch that year. I felt a lot of pressure on me really quickly because no one expected him to get injured.

"When I had to step in and hold it down a couple days I felt like there was a lot of pressure on me. It's the same thing -- you have to make good pitches. I got roughed up a couple times. I know it's hard but the situation was different then than it will hopefully be next year."

After locking down the Sept. 26 save in Houston his third in five chances this season Robertson said that he believes he will be better prepared for closing duties the next time around.