"A young Spanish player going into the National League could quite easily have been played on, but whenever teams did, he always came out the other side," Carden said.
The goalkeeper finished his tenure at Southport with a strong performance against Championship side Derby County in the FA Cup third round.
He left the pitch in tears after conceding a late stoppage-time penalty that ended the cup run.
"He was bitterly disappointed, but we all were, so that kind of tells you how much he felt at the time for the lads and the club," Carden said.
Carden concluded that Raya's performance showed he belonged at a higher level. "He made some saves in that game where we thought he's definitely at the level."
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Raya subsequently returned to Blackburn Rovers, gaining promotion from League One in 2017 before moving upward in English football.
