Gary Hamilton labelled Glenavon's performance "embarrassing" as they were left red-faced by derby rivals Portadown for the second time this season.
After the 4-1 defeat at Shamrock Park that saw them become a laughing stock for happy Ports players, Hamilton is demanding a response when they meet again on Tuesday following a display that he said let the club down.
It was a classic case of the form book going out the window in a derby as goals from Lee Bonis, Sam Warde, Ben Guy and Chris Lavery saw Portadown win for the first time in 12 games and end the Lurgan Blues' run of six matches without defeat.
It was also Portadown's first home Danske Bank Premiership win in almost four years, having last won in the top flight in April 2017.
"It's embarrassing," said a fed-up Hamilton.
"In two games now against our rivals this season, we've been beaten in both of them. They've scored four goals in both games and we haven't competed in either of them.
"I said to the players after the match that the club is really, really good to them - the directors, the Chairman, they look after them - and to put in two derby performances like that is unacceptable.
"We all know for the fans, the Chairman and directors, the derby games are the biggest games of the season and to let them down in the manner that they have in the last two is not acceptable and they need to go home this weekend and have a good long, hard look at themselves because they have to do better than that in derby games."
Bonis' back-post header put the Ports ahead on 27 minutes, nodding home Warde's corner that was the result of a neat passing move on the left.
Ten minutes later, Lee McNulty was adjudged to have stopped Stephen Murray's goal-bound shot with his arm, resulting in Portadown's first penalty of the season and a red card.
Warde converted from the spot and, at 2-0 up against 10 men and momentum very much on their side, Portadown really should have added to the score, with Bonis letting Glenavon off the hook when he hesitated with a shot after breaking clear of the defence.
After a superb through ball from Murray, Bonis then casually slipped it to Guy for the third on 61 minutes.
Sean Ward charged forward and hit a strike into the top corner to give Glenavon a consolation goal with 17 minutes left, but when Lavery hit Portadown's fourth with a low strike into the bottom corner, it was the Ports who had the last laugh - literally.
"When I was walking across the pitch at the end, there were four or five Portadown players laughing - they are entitled to laugh, they have just tanked us," said Hamilton.
"For me as an opposition player, that would stick with me and it wouldn't happen again. I have never been on a pitch in my life where I have had players laughing at me and that happened.
"The Portadown players are well within their rights to do it. I'm not having a go at them, but for our players to be on the opposition team having players laugh at them, if I was playing on Tuesday night I would certainly be looking to make amends and not be a laughing stock."
Not only was it Portadown's first home win this season, it was also their first top flight win under Matthew Tipton at Shamrock Park and it was a result and performance he savoured.
"The derby day win is for the fans because we only get three points whether it is Glenavon or someone else," said Tipton.
"The win is massively pleasing for me, but also the manner of our win.
"Our back-line was superb all game, Luke Wilson and Sam Warde controlled the midfield and we had fluidity in the front four."