The England Under-21 worldwide spent last season on loan at Norwich City, a club where his father Bryan Gunn also played.
MORE: Bye bye Angus.
Part of the Denmark squad that reached the last-16 in Russian Federation, the 25-year-old would appear a timely addition to a side yet to bring in a defender since Virgil van Dijk's world-record move to Liverpool. Hello Remi The youngster kept 15 clean sheets as he earned his first senior experience and has been capped 11 times at U21 level by England.
While a return to Norwich never seemed likely for next season, a loan move to top-flight Watford or Championship new boys Stoke had been touted.
Edging Fraser Forster out, and eventually becoming Players' Player of the Season, McCarthy will now face healthy competition from the arrival of Gunn, who recently turned down the opportunity from Scotland manager Alex McLeish to represent the national team, having been made eligible through his father. Former Reading keeper McCarthy has today been rewarded with a new four-year contract.
If he completes his move, Gunn could be joined at St Mary's by Denmark worldwide Jannik Vestergaard after Southampton agreed an £18m fee for the defender with German club Borussia Monchengladbach.
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