And the Blues boss backed the winger to show supporters his pacy threat and finishing quality, after taking up an option to extend his Fratton stay for another 12 months.
Reid is the fourth player whose option has been actioned, following in the footsteps of Marcus Harness, Louis Thompson and Jay Mingi.
The 21-year-old excited fans in pre-season after arriving on trial following his exit from Birmingham City.
But the former Manchester United and Swansea City youngster was dealt a massive setback when rupturing his knee cruciate ligament in a warm-up game at Luton Town last July.
It’s been a long road of rehabilitation for Reid since in the knowledge his deal was up this summer - but Cowley was clear he would always show loyalty to the player.
He said: ‘I knew the day after he did his cruciate at Luton we’d take up the option on him.
‘First and foremost, we have a moral obligation to do so - and secondly we just really believe in him.
‘We believe in him as a player and the qualities he has.
‘We believe in the speed he has in transition - and he’s a good finisher as well.’
The challenge moving forward for Reid will be to return in pre-season and work towards gaining some first-team minutes in the new campaign.
That is certain to present some challenges coming off the back of a serious injury which has required a long period of rehabilitation.
Cowley believes what Reid has been through in his time at Pompey would have seriously tested his resolve.
But the Blues boss actually believes that can offer some positives for the Luton-born man to take a relatively early stage of his career.
Cowley added ‘Jayden’s obviously missed a year, but sometimes when you have that disappointment it can fuel you for what’s to come.
‘Sometimes players can take football for granted and believe they are indestructible. That’s what youth can do to us.
‘What he’s been through in the last 12 months has been tough and he’s come back with a stronger mentality.
‘That’s what we anticipated Jayden doing.’