Carlisle manager Greg Abbott conceded his side's energy and performance levels dropped in their 4-1 defeat Leyton Orient.
The O's enjoyed a four-goal romp for the second time this season against the Cumbrians having also won 4-1 at Brunton Park in November.
On this occasion goals from Romain Vincelot, Shaun Batt, Dean Cox and a Kevin Lisbie penalty earned Orient the points over a Carlisle side that finished with 10 men after goalkeeper Mark Gillespie was dismissed in the second-half for a second bookable offence.
Abbott said his side could not match the performance levels from their previous two matches.
He said: "We are full of disappointment. In our two previous games, we put in an unbelievable amount of effort, energy and work and when you do that, you probably get the little bits of luck and decisions during a game that go your way.
"We found it hard to reproduce that and the key incidents and important decisions went against us at really poor times in the game and put us in a position where we couldn't recover from that.
"We've ended up getting beaten from a game that, beforehand, we really thought we had a chance of getting something from.
"We've met Orient on a day when they have hit really good form, we've got a lot of inexperience in our side and they bring an inconsistency.
"As a group, we've probably not worked as hard as we needed to for whatever reason, whether it's tiredness or fatigue, maybe the situation in the season is getting to some of the players.
"So there are all sorts of issues there that have contributed to us not being at our best."