A promising start to the new season, including briefly reaching top spot in the SPL, has come off the rails in recent weeks with no wins in the four games since Hearts were defeated in the Scottish Cup.
The visit from Celtic is followed by a trip across the city to face Hearts on January 3 with Fenlon well aware of the significance of both matches.
"It's a big week for us," he admitted. "Celtic at home and Hearts away are massive games, but they're great games to look forward to. We shouldn't have to worry about getting people up for the next two.
"We feel we're capable of getting something out of both games. It's important we approach them in the right manner.
"Retention of the ball against a team like Celtic is really important, your concentration levels have to be really high as well because they've got players in all positions that can cause you problems.
"We've got good players and they work tremendously hard. To be overcritical of them is not really fair.
"There's not many times where we've played here and not got to the tempo we want.
"We just need to make sure we approach every game in the same manner." Hibs' progress this season has been boosted by the loan signings of Leigh Griffiths, Ryan McGivern and Jorge Claros. All three deals expire next month with Fenlon already working on plan B should he be unable to extend the deals.
The Hibs boss said: "We are now at the stage where we have actively started to move on other options. We need to be able to bring in players if Leigh, Jorge and Ryan are not going to stay.
"I am confident that one or two of the loan players will stay. Whether we can keep the three, I'm not sure. We will probably have to move one or two out to bring new bodies in and we are trying to do that at the moment."
Celtic head to the capital in confident mood after stretching their lead at the top of the SPL to seven points with a 2-0 win away to Dundee on Wednesday night.
Charlie Mulgrew looks like missing out tomorrow with a rib injury with Neil Lennon expecting another tough test after Hibs drew 2-2 at Parkhead earlier in the season. "Hibs will be a tough proposition at home," the Celtic boss stated. "Pat has turned them around fantastically well.
"Easter Road is a good venue and I'm looking forward to the game. I would like to think we'll play better than on Wednesday and be stronger."