Ottawa looks to sweep the season series from the Lightning for the first time since 2005-06 when it visits Tampa Bay on Tuesday night.
The Senators (34-25-8) trail Northeast Division-leading Boston by three points, but they could be in first place if they hadn't struggled over the weekend.
Ottawa lost for only the second time in eight games Friday, 2-1 at home to Chicago, before opening a two-game swing through Florida on Sunday with a 4-2 defeat to the Panthers. The Bruins also lost both of their games over the weekend.
Prior to their consecutive defeats, the Senators had outscored their opponents 40-24 during a 7-3-1 stretch.
They jumped out to a 2-0 lead after the first period Sunday, but Robin Lehner allowed three goals in the first 11 minutes of the second.
"I think the whole team collapsed a little bit and they came out very hungry," said Lehner, who lost his second straight start after winning two in a row with a 1.00 goals-against average following his recall from the minors to replace injured Craig Anderson.
"Our competition level after the first period stayed the same and theirs obviously elevated to a higher level," coach Paul MacLean said. "Instead of raising our competition level as the game went on to meet theirs, we got frustrated."
The Senators haven't been frustrated much against the Lightning (31-28-6) this season, outscoring them 12-3 in winning all three meetings. However, Anderson shut down Tampa Bay in those matchups, and he won't be around for this one after badly cutting his finger while preparing a meal two weeks ago.
Lehner won't be around, either. Ottawa reassigned him Monday, recalling Ben Bishop from the minors to take his place. Bishop is 4-5-1 with a 2.83 goals-against average in 13 career games -- all with St. Louis, which traded him to the Senators on Feb. 26 for a draft pick. Veteran backup Alex Auld also remains on the roster.
The Senators, though, will have Daniel Alfredsson and Jason Spezza available. Spezza has four goals and two assists against the Lightning this season, while Alfredsson has two goals and three assists.
Alfredsson, however, will be trying to avoid going without a point for a season-high fifth straight contest, and Spezza had an 11-game point streak end Sunday.
Spezza registered his fourth career three-goal game in a 4-0 win at Tampa Bay on Feb. 14. He has 18 goals and 23 assists in 29 career games against the Lightning.
"I think it's the challenge of playing (Steven) Stamkos, (Vincent) Lecavalier, (Martin) St. Louis, you have to be on your game playing against those guys," Spezza said.
Stamkos leads the NHL with 47 goals, and he scored twice Saturday -- including in overtime -- as Tampa Bay beat Carolina 4-3 for its fourth straight win.
The Lightning have gone 14-5-2 in their last 21 games to get back into the Eastern Conference playoff race. Stamkos has 17 goals and 13 assists over that span.
"These guys are doing the impossible, so no matter how we do it doesn't make a difference," coach Guy Boucher said. "We find ways, and we'll take it."
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