The 19-year-old central midfielder made 33 league appearances for Northern Ireland outfit Glentoran last season and became the subject of interest from several English clubs in the ongoing transfer window.
But Portsmouth, who were keen on the youngster, managed to beat off stiff competition to land Devlin on a three-year deal.
Mousinho revealed that everyone at Portsmouth is excited about Devlin’s abilities and stated that the club believe that the young midfielder is ready for League One.
The Pompey boss outlined that Devlin has the capability to get into the opposition box and stressed that the teenager is good at laying on assists as well as getting himself on the scoresheet.
“Terry is someone that we’re really excited about not just for the future but for now as well”, Mousinho told the News.
“At 19 we think he can produce.
“He’s had an excellent season with Glentoran and definitely is a different mould.
“He’s an attacking midfielder, he likes to run, likes to get in the box and likes to score goals and get assists.”
Last season, the 19-year-old made a total of 41 outings for Glentoran, scoring six goals and providing two assists.
