Harlequins director of rugby Conor O'Shea lamented the champions' lack of intensity in Saturday's upset loss to Exeter at The Stoop.
The 27-16 defeat was Quins' second loss to the Chiefs this season after the 42-28 result at Sandy Park in October and could cost the lead in the Premiership standings of Saracens beat London Welsh on Sunday.
"That's the second time we've been outmuscled by Exeter," said O'Shea.
"There was never any massive intensity or energy in our play as they held on to the ball and won all the collisions.
"I'm frustrated as every time we edged in front we conceded a penalty, but all credit to Exeter as they kept coming and coming and ramped it up at the end. We were tired out with all the tackling we had to do as a result of coughing up possession."
With clashes away to both Saracens and Gloucester on the menu, Quins are in for a tough month ahead but O'Shea remained positive.
"It was not a train crash today; it's a long haul but we will have to rectify this performance as we face two tough games now but it's all about finishing in the top four and that is in our own hands," he said.
"When we lost at Exeter in October we went on a winning run of 10 games so we learn our lessons well."
Exeter coach Rob Baxter praised his team for their hard graft.
"We showed great intensity and a great work ethic especially in our defence as they are the top try scorers in the league," said Baxter.
"Today our performance was spurred by ambition not fear as we are safe from relegation."
With five games to go, Baxter still holds hopes of securing another Heineken Cup spot.
He said: "We saw today as the beginning of a cup run. We've taken nine points from the last two games and you soon move up the table. It was good to play on a firm pitch which suits us but I'm still frustrated by our loss at Sale as we should have finished that game off."