The academy graduate is in line to make successive appearances this week while Pompey’s No1 keeper is away on international duty with Scotland.
Bass will feature against Oxford in the EFL Trophy tonight and is expected to retain his starting spot for Gillingham’s League One visit to Fratton Park on Saturday.
As a result, Luke McGee will be called up to deputise on the bench.
Since his arrival from Shrewsbury in June 2018, MacGillivray has featured in every league game for the Blues.
But Jackett insists Bass can fill the void of the popular stopper.
The Pompey boss said: ‘Bass has been our No2 and has looked very good as well.
‘In terms of all young players, they deserve their chance and you have to put them in.
‘I am very confident and Luke is competing as well. Between the two of them, I do think that we have the week covered.
‘Alex is No2 and Luke is currently No3 and we have the week covered.
‘There has to be a time when you give young ones a chance – particularly ones that you like.
‘I do rate Alex Bass and he is a good goalkeeper. He’s got a good future ahead and I’m very confident of him stepping up, as well as Luke.
‘Young players have to go in at some stage. When the time comes, you have to put them in and particularly the ones you think can do it.
‘As the manager, I think Alex can.’
Bass will make only his second Football League appearance against Gillingham.
His league debut came in a 2-0 win over Peterborough on the final day of the 2017-18 season.
Despite his inexperience, Jackett has no concerns playing Bass between the posts.
'Alex has developed well,’ he added.
‘He says himself even though he hasn’t had a lot of games that he has got bigger and stronger all of the time.
‘Technically, he is a good keeper and I do think that he has got a good future ahead.’