Crystal Palace chairman Steve Parish admits the club made a mistake selling Glenn Murray to Bournemouth in 2015.
Murray joined the Cherries in a reported £4m deal and then subsequently returned to Brighton for a second spell in the summer of 2016 - initially on loan, before making the move permanent in January.
The 34-year-old fired home 23 goals to help Albion to promotion from the Championship last season and has already netted four times in the Premier League, despite a stop-start beginning to the campaign with an ankle injury.
Murray netted 56 goals in his first spell at Albion, before joining Crystal Palace on a free transfer in May, 2011. He scored 31 goals in the 2012/13 season, before his campaign came to an end in the first leg of the play-offs with a knee injury - sustained against Albion - but the Eagles still went on to be promoted.
They have been in the top flight ever since and travel to arch rivals Brighton for the first time since 2013 on Tuesday.
Parish, quoted by the Croydon Advertiser speaking at a Business Show in Olympia, said: "The fact that Glenn is not at this club is a massive regret for me.
"We made a mistake, simple as that.
"He did have a cruciate injury and I was told by managers he wasn't good enough and that he wouldn't make it. In the Premier League he didn't do this and he didn't do that.
"It's difficult. They are your football experts. I don't think they were doing it out of spite, that they didn't like Glenn - that's actually what they believed at the time.
"Maybe they hadn't watched him enough. Sometimes you don't realise people are good enough until they are given the opportunity."