With Tim Thomas now officially out of the picture for the Bruins, they truly become Tuukka Rask’s hockey club. Rask has responded well to that challenge while off to a 6-1-1 record with a 1.96 goals against average and a .922 save percentage in the first three weeks of the 2013 NHL season while working on a one-year “prove it” deal signed this summer. Bruins general manager Peter Chiarelli has been enthused enough with Rask’s performance that he indicated on Thursday the Bruins will be working to sign the 26-year-old goalie to a multi-year contract extension during this abbreviated 48-game regular season. The Bruins GM also shot down the notion there was a connection between Rask’s brilliant 20-save performance against the Habs on Wednesday night, and the deal jettisoning Thomas to Long Island less than 24 hours later. “Nothing is imminent and I can leave it at that,” said Chiarelli. “[The Thomas trade] has kind of been in the works for a while and it just coincidental that Tuukka had a terrific game last night.