The winger didn’t make a single appearance for the Blues after arriving on loan from Barnsley in January.
Isgrove was included in just three match-day squads and departed back to Oakwell before the League One play-off semi-final defeat to Sunderland.
The ex-Southampton man was subsequently released by the Tykes and moved to Swindon.
But Isgrove’s made a fine start to his County Ground career, having recorded four assists in six appearances.
According to Robins first-team coach Tommy Wright, the 26-year-old’s performances have drawn comparisons to Ritchie.
The Gosport lad left Pompey for Swindon in 2011 and has gone on to become a Premier League regular with Newcastle.
Wright told the Swindon Advertiser: ‘He has been popular since he came to the club. The fans like him.
‘Someone said he is like Matt Ritchie when he was here with that busy style – and look at what he has gone on to do.
‘You have got to remember that Lloyd has played at a higher level.
‘He scored in the play-off final at Barnsley when I was there, and he has played for Southampton and Sheffield Wednesday. He is a very good player.’