Lee Hodges says his Truro team have underachieved by a "country mile" by finishing the season one place above the National League South drop zone.
"I'm frustrated to say the least, but very pleased that we've stayed in this division," Hodges told BBC Cornwall.
"In a couple weeks time I'll be pleased we're still in this division, but we're going to have to raise the bar."
The Cornish side were safe going into their final game, which they lost 4-0 at relegated Bishop's Stortford.
"Well done for staying up," he added. "But we've underachieved by a country mile."
Having been play-off semi-finalists in 2015-16, after finishing fourth in the table, the White Tigers dropped to 19th in 2016-17, letting in 99 goals from their 42 league games, more than any other side above the bottom three.
Hodges says he will meet chairman Peter Masters this week to discuss plans for next season.
"There are a lot of decisions to be made on players," he said. "There's a few bonuses there for players who have done very well and competed, and others know that they've not been up to the standard."