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.

Daniel Sanzone was jailed for life after shaking two-week-old Joshua Millinson in Wolverhampton in 2015.
However, there was no evidence injuries that caused his death could have been anticipated, a safeguarding board said.
But it said staff were not questioning enough of the "concerning history" given by his parents.
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The review looked at two visits to New Cross Hospital's emergency unit by Joshua with Sanzone and the baby's mother, Zoe Howell, before the fatal shaking incident at their home in Pendeford.
Sanzone's trial had heard a nurse and a junior doctor assessed Joshua and found no swelling and no pain but later bone experts suggested he had suffered some leg fractures at this point.
However, the review found the fracture would have been very hard to identify in a baby so small and no X-ray was taken.
But the report said the conclusion that there were no safeguarding concerns was "reached too quickly" on a second emergency department visit.
It added although the evidence was "it was carried out competently, too much reliance was placed on the medical examination" of Joshua, which proved normal, and "insufficient account was taken of the concerning and inconsistent history given by his parents".
The review, commissioned by the Wolverhampton Safeguarding Children Board, made a total of 12 recommendations on how various public bodies could improve their practices.
It said the Royal Wolverhampton NHS Trust should review safeguarding arrangements in the New Cross Hospital emergency department and in antenatal services.
Wolverhampton City Council should also audit the effectiveness of local authority child and family assessment, the report said.
It added the National Probation Service in the Midlands should ensure risk assessments "are updated when there is a change in the circumstances of a supervised offender which may indicate a heightened possible risk to vulnerable children or adults".
Board chair Alan Coe said the report identified "a number of ways in which, in similar circumstances, more opportunities might be taken that could enable professionals to better coordinate and share information and to identify potential risks".
He said: "Actions are being taken, including the Royal Wolverhampton NHS Trust implementing new guidance for Emergency Duty staff about children who present with unexplained or inconsistently explained injuries, reviewing procedures in maternity services and updating training accordingly.
"[They also include] the council ensuring social care professionals clearly understand their responsibilities around pre-birth assessments and referrals and the National Probation Service ensuring that assessments are updated when there is a change of circumstances involving a supervised offender which may indicate a risk to others."
In November, Sanzone, 23, was convicted of murder and sentenced to a minimum of 15 years in prison.
Ms Howell was cleared of child cruelty and causing or allowing Joshua's death.
Warwickshire director of cricket Dougie Brown admits he cannot explain why his side's white-ball cricket has been inconsistent this season.
[NEXT_CONCEPT]
Hospital staff were too quick to assume there were no safeguarding concerns in the case of a baby who died after being shaken by his father, a report says.