That's because Barnsley have secured a place in the Championship play-offs this afternoon.
Reading's failure to defeat promotion-rivals Swansea means the Tykes are guaranteed a spot in the top six with two games of the campaign remaining.
The seventh-placed Royals were held to a 2-2 draw at the Madejski Stadium, with ex-Blues winger Jamal Lowe on target for the Swans.
Barnsley have enjoyed a remarkable rise after avoiding relegation on the final day of last season and not winning any of their opening seven games this time around.
Chaplin's featured regularly for Valerien Ismael's side, making 37 appearances and scoring three times.
Following 25 goals in 122 outings at Fratton Park, the academy product left Pompey for Coventry in the summer of 2018.
Jackett insisted he wanted to keep the forward, but reluctantly allowed him to leave.
Chaplin spent one season at the Sky Blues before he moved to Barnsley in July 2019. He signed a four-year deal at Oakwell.
Barnsley will play either Brentford, Swansea or AFC Bournemouth in the Championship play-offs next month.