Mark Robinson refused to use excuses after watching Sussex make their lowest Championship score for two years.
The county's unbeaten record in all cricket is under threat after they were dismissed for 143 on the first day by champions Nottinghamshire at Hove.
Only Matt Prior made more than 30 and Robinson admitted that his batsmen had not shown the neccessary application to survive on a slow pitch.
Cricket manager Robinson said: "I don't think there was a lack of effort but we weren't up to the challenge of trying to grind, graft and fight in what were not great conditions for batting.
"We've won two quite close games against Hampshire and Yorkshire in the Championship and mentally that and the volume of cricket we have had so far might have taken their toll but I would never use that as an excuse."
By the close Nottinghamshire had reached 72-2, leaving Sussex facing a salvage operation similar to the one they pulled off against Warwickshire last month when they batted for five sessions in the second innings to save the game.
Robinson said: "Warwickshire outplayed us for a day and half and we showed a lot of character to get a draw. I'd like to think we have it in us to do it again."
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