Kepa moved to Stamford Bridge on deadline day in August as a replacement for Madrid-bound Thibaut Courtois.
He had a relatively low-profile as far as Chelsea FC signings go, but Hislop has been following him since before his move to London and has always rated the 23-year-old.
He told ESPN FC: “What I’ve seen of Kepa in a Chelsea shirt, as with Athletic Bilbao, an incredible shot-stopper.
“I can’t think of many, well I can only think of four more, better than him in the league.
“I think that’s an outstanding acquisition by Chelsea.
“Watch that space, he may move up.”
Kepa ostensibly paid his own release clause from Bilbao, reportedly £71.6m, in order to join Chelsea FC, though Chelsea would have footed the bill for their new goalkeeper.
He became the world’s most expensive goalkeeper in the deal, passing the £56.25m that Liverpool FC paid for Alisson Becker just a matter of weeks before.
He had made 54 appearances for Basque team Athletic Bilbao, as well as appearing once for the Spanish national team and travelling as part of their 23-man squad for the World Cup in Russia.
He has kept two clean sheets so far during his time in blue, yet he could have had more had Chelsea FC’s defence looked less suspect.
He is part of the Spanish squad who will face England on Saturday in their opening game of the inaugural Uefa Nations’ League.
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