The issues that lie in front of Rangers general manager Glen Sather this summer are plentiful, and it all starts with the fact he has to shell out a lot of money at a time when the salary cap is coming down. By watching the spending limit drop from $70.2 million to $64.3 million next season, Sather has to find a way to wrap up three of the most important players on his roster, all of whom are restricted free agents. That list is absolutely topped by 23-year-old defenseman Ryan McDonagh, who has completed his entry-level contract and spent the whole of this postseason getting effusive praise heaped on him. “As I’ve always said about Ryan, if he makes a mistake, it does not affect him,” said coach John Tortorella, who also began using the shutdown blueliner in more offensive situations, including the power play. “It doesn’t take him five shifts to get it back. He’s ready to go the next shift and I think that’s part of the intangible that he has, a mental toughness. I think he is one of the best of that on our team.” Although Sather often likes to give two-year “bridge deals” to restricted free agents — like the two-year, $5.1 million contract he barely got done for defenseman Michael Del Zotto before this season began — a longer and more lucrative deal might be in the works for McDonagh. After him comes top center Derek Stepan and speedy winger Carl Hagelin. Closely following the top three is Mats Zuccarello, also a restricted free agent. * More money would be available if Sather uses his second and final amnesty buyout on center Brad Richards, who is owed $6.67 million per year through 2019-20. The 33-year-old winner of the 2004 Conn Smythe Award had his game fall of so precipitously, he was a healthy scratch for the final two games of the playoffs.