David Robertson, who has not discussed a contract extension, said he is content to finish the season before talking to the Yankees about his future and said the team might have saved itself money had it attempted to sign the closer last winter. “I thought the calls would come but at this point right now I am going to wait and see how the season plays out,’’ Robertson said before the Yankees’ 5-1 win over the Tigers Wednesday at the Stadium. Asked if he would ignore an offer and wait to become a free agent following the season, Robertson didn’t shut the door completely but explained the offer would have to be significant to discuss it. “It would have to be a legit offer at this point of the year,’’ said Robertson, who has converted 30 of 32 saves and has proved to everybody that replacing Mariano Rivera wasn’t too tall of a task. With Rivera gone after the 2013 season and Robertson the apparent replacement, he would have considered staying for less. “This offseason I probably would have gone for a discount, although I wasn’t a closer,’’ said the 29-year-old right-hander, who is making $5.215 million in a walk year. The Yankees aren’t known for locking up players before they hit free agency, but they have done it. This past spring training they signed Brett Gardner to a four-year deal worth $52 million that starts in 2015 to keep him off the free-agent market. Gardner said he didn’t want the hassle of being a free agent. General manager Brian Cashman gave a “No comment’’ when asked if the club would make an offer to Robertson before the end of the season.