It was assumed that rookie Chris Kreider would come out of the Rangers lineup then, but his increased confidence and Boyle's injury could change those plans.
Now New York's special season hangs in the balance in Game 6.
"Win that one and bring it back here," Rangers forward Brad Richards said. "It's just going to take seven games now. That's the reality."
The Rangers fired 15 shots at Anderson in the third period, but couldn't get a puck past him — even during their fourth power play of the night.
Senators coach Paul MacLean said this was the best he has seen Anderson, who set the club record for saves in a playoff shutout.
"To shut a team out on the road is pretty tough to do, especially in the playoffs in this atmosphere," Spezza said. "When Andy is seeing the puck well and seeing things from the outside, that's when he's at his best.
Spezza netted his first goal of the series 9:18 in off an assist from teenager Mark Stone, who made his NHL debut after playing junior hockey last week.
In the previous four games, the Rangers trailed only twice — at the end of overtime in their two losses. Coming from behind hadn't be part of New York's plan until Spezza broke out of his funk with his first goal of the series.
About 30 seconds after Ottawa killed its first short-handed situation of the opening period, Spezza gave the Senators their first in-game lead in five games.
Filip Kuba sent a pass from the Senators' end of the ice up to the neutral zone to Stone, who filled in for injured forward Jesse Winchester (upper body). Stone waited just outside the Rangers blue line and then made a short pass in front of him to Spezza at the bottom of the right circle. Spezza, who had 34 goals and a team-high 84 points in the regular season, showed off his scoring touch by deftly snapping a shot between Lundqvist's pads.
"The play was made by Mark Stone," MacLean said. "To make a play like that on his first shift in the National Hockey League is pretty impressive."
Spezza let out a roar and emphatically punched the glass in the corner, as if to release the remaining bit of frustration that grew during his drought.
The nervous Madison Square Garden crowd quickly became quiet and stayed that way for much of the rest of the first period, except to cheer a few big hits by the Rangers and to boo after New York's third failed power play at the end of the frame.
The Rangers had their chances to score first for the fifth consecutive game, or get even, but their power-play woes did them in again. After failing to score on a hooking call against Sergei Gonchar, and an interference penalty on Jared Cowen, New York nearly gave up a short-handed goal after Spezza went off for roughing up Rangers captain Ryan Callahan with a gloved punch to the face during an after-whistle scrum.
Defenseman Dan Girardi made a pass along the blue line, leading to a breakaway by Erik Condra, that was snuffed out by Lundqvist after Condra lost control of the puck during his sprint up the ice.
The power plays shifted in Ottawa's favor in the second period, but the Senators couldn't take advantage of the three they got, either.
Ruslan Fedotenko went off for high-sticking in the opening minute, Mike Rupp was called for charging Jim O'Brien with 6:12 left, and Callahan went off for roughing when he came to the defense of Marian Gaborik, who was knocked to the ice by a late hit from Ottawa's Colin Greening that went unpenalized.
Lundqvist was particularly sharp in the second, making 12 saves — including a handful of tough chances created by misplays by his teammates.
NOTES: The 19-year-old Stone helped Canada win the silver medal at the World Junior Championship. ... The Rangers' power play was 1 for 11 in the opening three games of the series before a pair of goals in the first period of Game 4 gave New York a 2-0 lead. But since then, it has failed on nine straight chances.