Rask stopped 18 shots in the first period, after making a career-high 59 saves in the opener. His most impressive save came six minutes in when he robbed Nick Leddy with a quick glove.
Despite their limited scoring chances, the Bruins were able to tie it 1-1 in the second period on a Kelly goal at 14:58. A turnover behind the Chicago net was grabbed by Paille, who skated to the front and fed Kelly for his first goal of the playoffs.
"On my goal, it was a great five-guy effort," said Kelly, who hadn't scored since April 17 against Buffalo. "Andrew (Ference) made a pinch, Tyler (Seguin) was in on the play and got it to Daniel, and Daniel took it to the net. I just happened to be there, tapped it in."
Marchand nearly gave the Bruins the lead late in the second period on a short-handed chance. He beat Brent Seabrook to a loose puck in the Blackhawks' zone, but his shot hit the post to Crawford's left.
NOTES: Horton was back in the Bruins' lineup despite leaving Game 1 on Wednesday night in the first overtime and not returning with a reported shoulder injury. ... Sharp (6) and Marian Hossa (5) had more first-period shots than the Bruins (4). ... Teams that have taken a 2-0 lead in the Stanley Cup Finals are 32-3 all time, but two of those losses came in the past four seasons. The Bruins lost the first two games to Vancouver before rallying to win the 2011 Stanley Cup. ... There hasn't been a split of the first two games in the Finals since 2004.