Matt Tubbs netted the only goal of the game at Northampton and home boss Gary Johnson admitted afterwards that his team did not do enough to warrant getting a result.
Evans agreed but told the official Crawley Town website that the scoreline meant he could not relax at any point.
"You are always fearful that the opposition might get a goal out of nothing."
Northampton now lie 15th in League Two with the same number of points, taken from 12 fixtures to date.
They return to action on Friday night when Johnson takes his side to the Potteries to face Port Vale. Check out the head-to-head record of the two sides by clicking below.