Manager Lewis Thorogood felt frustrated after a second-half collapse by Spalding United’s under-21 development team.
They were beaten 4-1 by FBT International Academy at Eastwood on Sunday after taking the lead through Andy Brigham.
Thorogood said: “We knew they were going to be a very good outfit because they are run by the former academy manager at Chesterfield.
“We had a couple of players missing through injury but we looked comfortable in the first half after going 1-0 up.
“We did well for about 20 minutes in the second half and missed an absolute sitter.
“They were a physical side with a lot of pace and we gave away a penalty.
This week there is going to be more reorganisation with a couple coming in and a couple going out.Lewis Thorogood
“After the equaliser, our heads went down and they picked us off.
“It was frustrating because we look good going forward but we need to sort out those individual errors.
“That’s what pre-season is all about and getting it right.
“This week there is going to be more reorganisation with a couple coming in and a couple going out.
“I’m happy with the nucleus of the squad but there is work to do.”
The final pre-season friendly is away to Eastwood on Friday.
Spalding will be playing in the Lincolnshire FA Under-21 Development League’s south section.
The first game is due to be at home to Thorogood’s former club Boston United on Tuesday, August 29.