It will be a first game for the region since March 1 when they were defeated in Italy against Zebre.
John - who has taken over control of first team affairs with Dale McIntosh following the resignation of Phil Davies - insists that break has helped the squad as they prepare for the final six league games.
He said: "The break has been good and has given us the chance to regroup and refocus.
"We have taken stock and it has given a bit of time for me and Dale (McIntosh) to look at the situation and our game.
"Our roles have changed a little bit now Phil has left, but the time that we have had has allowed us to meet the board and players, to get a structure in place over these two weeks. It has been beneficial to us.
"We will get on with the job in hand and hopefully we will get a positive result on Friday at Ospreys.
"We roll our sleeves up and get on with it. It's a big game for us to get back into the league season. After the debacle at Zebre, it focusses people's minds with a local derby.
"It's good to play a team like the Ospreys and the boys have got to give everything they have got."
Two players Blues will miss for the game are Sam Warburton and Leigh Halfpenny, after they both injured their shoulders on international duty.
"Naturally we are disappointed that Sam and Leigh will not feature in these last six games," added John. "But the squad is good enough to pick themselves up and take the opportunity they now have over the next six weeks."