But there's more than 90 minutes to play.
After the West Ham match on Saturday, Spurs boss Mauricio Pochettino said Kane was "one of the best strikers in the world".
"The return of Harry Kane is very important as he brings a lot of positive energy", the goalkeeper told a media conference.
"West Ham made it hard for us, they shut off the middle of the pitch and we had to be patient. Hopefully he will be decisive on Tuesday".
"You see how we play in possession, we play 3-4-3, or 3-3-1-3".
Kane has played twice since his comeback from a seven-week ankle injury lay off, scoring three times.
Dembele has been hampered by a niggling foot problem for several weeks and after making his comeback against Arsenal two weeks ago, he was withdrawn in the 72nd minute against West Ham as Pochettino tries to protect his Belgian midfielder.
The 23-year-old, sent back from England duty last weekend in order to build up his fitness, tucked in an 89th-minute cross from Son Heung Min to equalise. "If you take one video, and analyse a little bit, you realise that we play like with three centre-backs".
"It's a very important day to assess and see if the players are fully recovered".
Two defeats at their adopted Wembley home have left Tottenham in a precarious position; failure to beat Monaco at Stade Louis II on Tuesday coupled with Bayer Leverkusen defeating CSKA Moscow will make it impossible for Spurs to reach the tournament's knockout phase.
"It's a game that we must win but we need to find a way how", Pochettino said.
The goal rattled the hosts, who struggled to get their game together in the rest of the first half and never really looked like getting back on level terms.
"We don't want to take risks with them".
"That's our idea, our challenge".
Lloris also moved to ease concerns about his future. The goalkeeper is yet to extend his current contract, which expires in 2019, but insists he is happy at White Hart Lane.
The 23-year-old's current deal runs until 2020 and sees him earn nearly half as much as worldwide colleagues Jamie Vardy and Daniel Sturridge - who both take home upwards of £100,000-per-week at Leicester and Liverpool respectively.
"Now it's the complete opposite". We're full of momentum. It was a great game and we tried everything to win but in the final few minutes we lost the points.