The Bears face must-win games in their final group matches in the T20 Blast and One-Day Cup to keep alive hopes of making the quarter-finals in both.
"There's no reason why it should be inconsistent, we know what we're meant to be doing," Brown, 46, told BBC WM.
"Under pressure, we're failing to deliver what we're supposed to."
Warwickshire's four-wicket defeat by Durham, who chased down 293 to win, leaves the third-placed Bears needing to beat current leaders Yorkshire on Monday to stay in the hunt for the last eight.
Before then, they go to Old Trafford on Friday knowing victory over Lancashire in their last T20 Blast game is vital to their chances of making the knockout stages.
Brown is confident the high-stakes nature of the next two matches will bring out the best in his side.
"We are a decent side - we're struggling a the moment as we're struggling to get the same team out on the park twice," Brown said.
"The guys who come in should be proficient at executing under pressure  - that's what we haven't done and that's what we need to do in these two games.
"We know we've got to win them and it's exciting to be part of."
All-rounder Keith Barker is set to return after injury at Old Trafford, while former England batsman Jonathan Trott could make a comeback against Yorkshire following a back problem.
Warwickshire director of cricket Dougie Brown admits he cannot explain why his side's white-ball cricket has been inconsistent this season.