Jurgen Klopp's side will feature in the Premier League and Carabao Cup as well as the Champions League and the FIFA Club World Cup in December.
Former Tottenham midfielder Jenas believes Liverpool have struggled for form and must improve if they want to cling on to top spot.
Speaking exclusively to RadioTimes.com, Jenas said: "My worry for Liverpool is that I feel like they're struggling for form more than anything.
"People will say it's a huge positive that they're 'not playing well and winning games' but they're having some huge slices of luck with VAR decisions going their way, last-minute winners.
"Yes, it takes that to win a league, but can it continue?"
While Jenas – who will feature as a pundit on Amazon Prime's live Premier League coverage over the Christmas period – is wary of Liverpool's upcoming run, he does believe that success in the next few weeks could define the Reds' season.
He said: "Liverpool have got a huge amount of fixtures coming up over the festive period in the Premier League and Europe fixtures as well, how can they get through it? Can they get through unscathed?
"If they do, come mid-January they'll be in a position where I can't see anyone taking the league off them."
Fabinho has been ruled out until 2020 in a significant blow for Liverpool, but Jenas believes they do have the depth to cope through testing times.
He said: "The depth is there, player-for-player, so if Wijnaldum comes out they've got Keita or Milner that can fill in.
"Lallana's still there, Alex Oxlade-Chamberlain too, so they've got plenty of bodies.
"Still, that game at the weekend against Crystal Palace with no Salah... They just don't function the same without that front three.
"Oxlade-Chamberlain played well, he was probably the better player of the three, but something about having to put Mane on the right, it just doesn't seem to function well."
Check out RadioTimes.com's full guide to watch Premier League football on Amazon Prime this Christmas
