Matt Mayes, Dan Smith and Matt Casey have all moved to Privett Park on a work-experience loan and all three will be in the squad for the trip to Redditch United on Saturday (3pm).
Young Blues captain Mayes is a striker, Smith is a winger and Casey is a towering centre-back.
Catlin told Kevin Ricketts of The News: "I feel we need some extra bodies to come in at this stage.
"They all played for Pompey Academy in their FA Youth Cup tie against Leicester City on Tuesday. Pompey Academy don’t have any games over the Christmas period so it was felt they can gain some good experience with us.
"I am taking them on a work-experience loan and it can work for both clubs. Pompey can see how they cope with men’s football and it helps us out.
"Our loan striker Conor Davis is due return to Reading on December 15 and defender Lee Molyneaux is due to go back to the Hawks at the same time. If I can’t extend their loans then at least I will have the Pompey players."
Updated 11:47 - 7 Dec 2017 by Site Manager