John Mousinho on the 'pivotal' figure driving Portsmouth promotion bid - and he last played a decade ago

While many were surprised at John Mousinho’s appointment as the Blues’ head coach, similarly the rookie boss’ choice of a 43-year-old right-hand man also raised eyebrows.

Arriving after a decade in Chelsea’s Academy, Jon Harley’s February employment represented a return to Fratton Park following a short-lived playing spell.

Having attended the same Uefa Pro Licence course at St George's Park, Mousinho had put the ex-Chelsea, Fulham and West Ham left-back’s name forward as a potential contender as assistant head coach.

Now, eight months later, the duo have masterminded Pompey’s rise to the top of League One and a remarkable 23-match unbeaten league run.

Mousinho told The News: ‘Jon has been pivotal in everything we’ve tried to do.

‘He’s an unbelievable character to have around the place, he lifts the lads, lifts the staff, and, most importantly, is an excellent coach and excellent tactician.

‘If you ever bother looking at my nervous wreck of a match-day, it is back and forth with Jon and Zesh Rehman, asking for advice, they see loads that I don’t necessarily pick up. He has been absolutely brilliant.

‘He had the under-21s role at Chelsea and been in various different departments there over 10 years, but this was something he wanted to do. Jon took that leap of faith.

‘He would have had a very comfortable job at Chelsea, probably for as many years as he wanted to have it. Stepping into the world of coaching in football is a pretty unstable place to be.

‘One of the things we thought about Jon is even though he wasn’t experienced at league level, he was experienced at coaching.

‘I have a huge amount of experience playing at the Championship, League One and League Two since 2005, but the one thing I probably didn’t have a huge amount of exposure to was actually coaching

‘Even though I had been a player-coach for a couple of years, that’s not long in the game to be honest. Yet Jon had that level of experience I didn’t have – and it has shown to have worked pretty well so far.

‘He is very, very bright and energetic, a funny and bubbly guy, I’ve never seen him have a down day, he’s always there to pick you up in tough times.’

Harley represented Pompey 26 times in the first half of the 2012-13 campaign, before his contract wasn’t renewed in January 2013.

I represented his final Football League club – and heralded the start of a coaching career which would bring him back to the south coast 10 years later.

Mousinho added: ‘Jon contacted me once I got the job congratulating me, yet I actually knew before that conversation he was someone I wanted to approach.

‘We went through an extensive interview process for this role and interviewed a range of people from different backgrounds and different ages. Age wasn’t something we particularly looked at.

‘Ultimately, have they the ability to do their job, have they the enthusiasm, is there a huge amount of upside – and, of course, Jon ticks all those boxes.’