Chris Kreider’s road to number retirement has hit a speed bump. The 21-year-old winger, who created a singular sensation last spring by scoring five goals in the playoffs directly out of Boston College, was assigned by the Rangers yesterday to the AHL Whale after having been a healthy scratch for Thursday’s 4-3 shootout defeat to the Islanders at the Garden. Kreider, who missed five games from Jan. 24 through Feb. 2 with bone chips in his right ankle, recorded two points (1-1) in seven matches with the Rangers, scoring his first NHL regular-season goal against the Devils and Martin Brodeur in Newark on Feb. 5 in what was by far the rookie’s most impressive game of the year. But that’s because Kreider was assertive in that game, using his speed to force the issue and his skill to create. For the most part, however, that was the exception to the rule. The winger seemed tentative, tip-toeing rather than initiating through most of his shifts as if fearful of making a mistake. Kreider’s demotion leaves the Blueshirts with 12 legitimate forwards on the roster in anticipation of tomorrow night’s match at the Garden against the Capitals, who have won three straight. That group of forwards includes 19-year-old J.T. Miller, whose Entry Level contract will kick in when he plays his next game. Defenseman Stu Bickel, who has played the wing, is also on the roster. The Rangers are hardly obsessing over Miller’s contract situation. Even if the Blueshirts should decide either to dress Bickel up front or make another move before tomorrow night and return Miller — who played only one third-period shift on Thursday — to the Whale, chances are overwhelming he would be recalled after getting more work in the AHL.