The striker has endured a desperately disappointing maiden season with the Blues.
And his ongoing presence in Paul Cook’s squad is under scrutiny as Pompey begin to prepare for life in League One.
Main has another 12 months on the contract he signed in July 2016 after arriving from Doncaster for an undisclosed fee.
That deal also contained the option for a third season.
However, the striker could depart this summer as Cook strives to revamp his side following promotion.
The last of Main’s 14 Blues appearances arrived in October before he was struck down by injury.
The precise problem was largely difficult to diagnose before it was eventually pinpointed as a back issue.
Main returned to training in March and has worked hard to bring himself up to speed with his Pompey team-mates.
He has since served as an unused substitute in the victory at Notts County which won promotion to League One.
The 24-year-old was also granted a 13-minute cameo off the bench in the reserves’ Premier League Cup victory over Colchester earlier this month.
However, he failed to make the match-day 18 for Saturday’s visit of Cambridge United, in which Nicke Kabamba was granted a full debut.
Cook urgently needs to strengthen his striking pool in the summer.
Noel Hunt is out of contract, loanee Eoin Doyle must return to Preston and Michael Smith has spent the second half of the campaign at Northampton.
Meanwhile, forgotten man Main has five goals in 14 outings.