How much could have been expected of Roman Hamrlik, the 39-year-old veteran defenseman who made the most galling mistake in the Rangers’ season-ending, 3-1 loss to the Bruins in Game 5 of the Eastern Conference semifinals last night at TD Garden. With 13 minutes gone by in the second period, the game was tied 1-1 and the puck came to the stick of Hamrlik. Hamrlik, who had not played since April 1, was inserted into the lineup in Game 4 as Anton Stralman still reeled from an undisclosed injury. In his 113th career playoff game, at the end of his 20th NHL season, Hamrlik collected the puck and tried to make a pass through traffic up the middle. Instead, he turned it over. The Bruins rushed down the ice, and Hamrlik couldn’t stop fourth liners Daniel Paille and Shawn Thornton from slicing through the zone, the puck eventually rolling to Gregory Campbell, who lifted it over Henrik Lundqvist’s shoulder for a 2-1 Boston lead. “I tried to put it in the puck in the middle and it was a turnover,” Hamrlik said. “They brought it to the net and scored a big goal.” Hamrlik was placed on waivers by the Capitals late in the season, and now is an unrestricted free agent contemplating retirement.