Although Rotherham lost by eight tries to one, Burnell said there was plenty to be pleased about as the Titans were playing against a top quality Premiership team which included the French international, number eight Louis Picamoles, and England centre Luther Burrell.
But Burnell admitted: “I was disappointed with the number of errors. We played well for 50 minutes but you have to do that for 80.
“The mistakes let us down at crucial times but we will learn.”
Rotherham fielded nine new players, including flanker Laurence Cowen who scored the Titans only try which gave them an early lead.
But the class of the Premiership club gradually wore the Titans down and while they competed ferociously for an hour, Northampton’s power and speed could not be matched.
Rotherham’s efforts should have been reflected by more points in the first half, but new fly half, Charlie Foley signed from Moseley, missed the conversion of Cowen’s try and two penalties.
Rotherham, who begin their Championship campaign at Clifton Lane in two weeks against London Welsh, have a final pre-season match at Hull Ionians this Saturday.
It’s thought that once again Burnell will take a large squad to Hull so that he can have another look at his players before deciding the match day group for the London Welsh game.