Under-18s boss Harris takes charge of the Blues’ second string alongside first-team coach Ian Foster for the group-stage clash.
The visitors are expected to name a strong side, with a number of senior players handed precious game time.
Youth is also set to be given a chance against the Robins, though, and Harris believes the competition can be of great benefit to all parties.
He said: ‘The idea behind entering the Central League Cup and the Premier League Cup is to give senior pros who need game time, some game time.
‘It is also to blood a few of the Academy lads and give them what would probably be considered the next level up in terms of their development.
‘Bristol City will use the game as a development tool – I don’t know whether Lee (Johnson) will drop in any of his first team who need a run out, we will see this afternoon.
‘But it is a great experience for our boys and for them to play with the first-team lads.’
A trio of second-year scholars are likely to be named in the Blues’ starting XI at Championship side City’s training ground.
And with more named on the substitutes bench, the opportunity is there for Pompey’s youngsters to make a positive impression.
Harris said: ‘The boys are always asking whether any of them are likely to be involved in these matches.
‘They are keen to test themselves at that next level, which is obviously important.
‘And it’s important that when they do get opportunities, like today, they step up to the plate and show what they are all about.’