This may be the worst the Bruins have looked in 11 games under Bruce Cassidy.

With a chance to match the Ottawa Senators in the standings on Monday night, the Bruins came out flat in an important four-point game against their Atlantic Division foes.

Despite a late surge, Cassidy’s squad wasn’t clicking as much as it has in the past. Their 4-2 loss in Canada’s capital city proves that there’s still plenty of work needed to do with a little more than one month remaining in the regular season.

Here is what we learned as the B’s fall to 8-3-0 under their interim coach.

A rare uphill climb from the get-go

In all but two occasions with Cassidy at the helm – both in the last three games – the Bruins have scored the game’s first goal. In all but one occasion, the Bruins also notched a goal in the first period. The latter happened tonight when Patrice Bergeron scored his 16th late in the opening stanza. The former put the B’s behind the 8-ball.

Although they had a 13-7 advantage in shots on goal, the Bruins spent most of the period battling the puck on both ends of the ice. Doing so in an early 2-0 deficit thanks to goals from Derick Brassard and Jean-Gabriel Pageau just 2:04 apart in the opening 3:25 gave the Sens the boost against a Bruins squad that had their share of issues solving Guy Boucher’s 1-3-1 system all night long.

Second period a momentum killer

The Bruins were fortunate to stay within a goal in the middle stanza.

At a time where icings, long shifts and extensive zone time in the defensive end were prevalent, the B’s have Tuukka Rask to thank for keeping them in it. Bouncing back from a rough first period, especially after the soft goal allowed on Brassard’s opening tally, Rask made 16 stops in the middle 20 to keep the Black and Gold within striking distance.

Too little, too late

Trading power play goals 1:16 apart, the Bruins remained within one after Brad Marchand responded to Mike Hoffman’s laser past Rask. Marchand’s tally marked his second straight 30-goal season and is seven goals removed from matching last year’s career high.

With David Pastrnak moving up with Marchand and Bergeron, the Bruins had their biggest push of the night as they looked for the equalizer. Unfortunately for the aforementioned trio, the other three lines couldn’t sustain much pressure in the attacking end as much.

With David Backes moved down to the third line with Ryan Spooner and Frank Vatrano and new addition Drew Stafford skating with Peter Cehlarik and David Krejci – with the fourth line of Dominic Moore, Tim Schaller and Riley Nash still intact – Cassidy couldn’t get the spark that he needed from the line changes. Trade deadline acquisition and perennial Bruins villain Alex Burrows secured the Sens’ second victory over Boston this season with a late empty-netter.

Whether or not the line changes will be a short-term thing or a long-term solution remains to be seen. Even with the hiccup in Ottawa, it may not be a bad thing for Cassidy to roll with these lines come Wednesday night when they host the Red Wings.