Stevenage boss Graham Westley says he would have taken the club to the Championship had he not left in 2012.
Boro failed to get promoted despite being sixth in League One when Westley quit to join Preston, and he returned to the now-League Two club last year.
"Stevenage are a small club in League Two. I never believe in putting limits there," he told BBC Look East.
"I honestly think had I stayed here when I went, we'd have gone into the Championship."
He added: "But Yeovil went into the Championship and went straight back down and are now at the bottom end of League One.
"We all want success again. But the way you get success is to patiently and diligently work together."
Stevenage suffered relegation to League Two last season, in what was Westley's first full season in charge since his return.
It is his third spell as manager of the Hertfordshire club, with his previous stint producing back-to-back promotions from the Conference to League One.
Boro are currently 15th in the table, but have won three of their last six league games.
"Stevenage being in the Football League is overachieving," said Westley.
"If you look at the fanbase, we'd be right down the bottom of League Two in terms of attendance.
"We have to do a lot right to compete with and be better than the Plymouths, Oxfords and Portsmouths."