Newcastle manager Alan Pardew said his misdemeanour at Hull City in March was the catalyst for the club's poor run-in.
After their resounding 4-1 win at the KC Stadium, the Magpies lost seven of their next eight games, before beating Cardiff City 3-0 in their penultimate league clash to sew up a top-10 finish.
However, Pardew - who is under pressure to retain his job - took responsibility for his side's season, claiming his headbutt on Hull midfielder David Meyler was the beginning of the end for the Tyneside outfit.
"It's a contrasting season. The first half, I actually felt we played not far from our top level for most of that," Pardew said.
"But in the second half we haven't been good enough, I haven't been good enough and the results have followed.
"I've obviously let myself down on the touchline, for sure.
"The Hull incident was obviously a turning point I definitely didn't want to have. I think that affected me and the team.
"I will make sure that never happens again. It stands out, if I'm honest, from anything else."
Pardew said he did not believe reports Newcastle had approached Saint-Etienne coach Christophe Galtier.
"I don't know who he (Galtier) would have spoken to, but there are only one or two people who really matter here and I don't think they have spoken to him. But that is part of business," he said.
"Chairman, chief executives, managers, will all have a look at this season and draw breath a little bit, about how to go forward together and make sure that everyone is doing it with honesty and integrity.
"I think a couple of managers lost their jobs this year when really and truly, were they treated with the right integrity and honesty?"