That’s if this season’s stats are anything to go by.
The Blues have been on the receiving end of an ex-player scoring against them eight times during the current campaign.
And on each occasion that has happened, the goals have contributed to Kenny Jackett’s side failing to win the match in question.
In fact, the record shows that the Blues have lost five of the six games this has happened, with a solitary draw the best they have mustered when a former Pompey player has registered against them.
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That stalemate came in last month’s 2-2 draw with Doncaster Rovers.
John Marquis, who spent a month on loan at Fratton Park during the 2013-14 season, handed Donny a 2-1 lead on 63 minutes, before Brett Pitman rescued a point.
But no rescue mission has materialised in the five other matches when an ex-player has returned to haunt his former club.
Greg Halford and Nathaniel Mendez-Laing both scored when Cardiff knocked the Blues out of the Carabao Cup back in August.
Halford was a fans’ favourite during two spells at Fratton Park between October 2010 and July 2012, with the first a loan move from Wolves.
Laing was a loan signing from Peterborough during the 2012-13 season, but failed to score during his eight appearances.
Four days after the former Pompey duo struck, Wes Thomas did the same when the Blues lost 3-0 at Oxford.
The striker, who scored three goals for the Blues in six appearances during the 2012-13 campaign, opened the scoring at the Kassam Stadium.
Conor Wilkinson is the most recent ex-player to turn the tables on Pompey, with the Irishman netting in Saturday’s 3-1 defeat to Gillingham.
He was signed on loan by Paul Cook during the 2015-16 season from Bolton, but made only one appearance.
Before that, left-back Joe Mattock – seven loan games for the Blues during the 2011-12 season – popped up with a late winner for Rotherham in January.
And then there’s Doyle, who scored both goals in Oldham’s 2-1 victory at Fratton Park back in September.
That double equalled the number of goals he scored during last season’s loan spell from Preston.
Since then, the forward has netted a further nine times for the Latics, taking his tally to the season to 15.
The Blues have been warned!