Dan Barrett accused his Boston Town side of taking their foot off the gas as they were beaten 2-1 by AFC Kempston Rovers on Saturday.
Alex Beck handed the Poachers a second-minute lead as he netted his seventh goal of the season, only for the Walnut Boys to come from behind to win with two strikes after the interval.
“Saturday was our worst performance in the last 10 games,” manager Barrett said.
“We started off well and scored a goal early on.
“We were the only team in it for the first 15 minutes and should have been 2-0, if not 3-0, up.
“We took our foot off the gas and we should have gone in at half time at 1-1 or 1-2, they missed some good chances.
“We didn’t come out in the second half and they continued on from where they left off, but this time hitting the back of the net.
“They thoroughly deserved to win.”
Shane Bush and Dom Marsala both netted for Kempston after the interval to secure the points.
The Poachers now face a UCL Premier Lincolnshire derby double, travelling to Deeping Rangers on Saturday (KO 3pm) and Sleaford Town on January 6.
Barrett is demanding better from his side.
“We have a very hard task on our hands over the next few weeks if we perform in the same manner,” he added.
Pictured is Tim Lowe in action on Saturday.