The Blues’ opening game of the 2020-21 season has been rearranaged from Saturday, September 5 to Saturday, August 29.
As a result, Kenny Jackett’s side have scrapped their friendly against Bristol City.
And Stevenage have claimed it’s because a Pompey player will be on international duty the following week.
That looks likely to be Ronan Curtis, who will be recalled to the Republic of Ireland squad.
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Ireland have Nations League fixtures in Bulgaria (September 3) and Finland in Dublin (September 6).
Curtis was dropped from Eire’s last meet-up in November after suffering a dip in form at the start of last term.
However, he bounced back superbly and finished the season with 14 goals and 12 assists.
Stephen Kenny is now in charge of Ireland after taking over from Mick McCarthy in April.
Curtis worked under Kenny during his time as Eire under-21s manager.