The England international striker has been out of action since April 9 after picking up an untimely ankle injury.
He has nursed his way back to health ahead of a European showpiece in Madrid, with Mauricio Pochettino facing a big selection call before taking on Liverpool.
Mertesacker believes the Spurs boss should be keeping faith with those who have got the club to this point, even when taking into account the presence of a prolific frontman.
The ex-Arsenal star told DAZN: “It was definitely thanks to the whole team that they reached the final. Suddenly you had Heung-min Son being on fire when Harry Kane was out. He scored a lot of goals. Then there was Lucas Moura scoring a hat-trick [against Ajax in the semi-finals]. They gave players space for development and they took the next step.
“Now Harry Kane comes back and the coach has to ask himself what to do. It really is a difficult decision. I would keep the things which have worked out in the last games and change not too much as the players have deserved it.”
Pressed further on whether he would snub Kane in his starting XI, Mertesacker added: “Yes... If I were the coach I would do that.
“Yes, I think it will be a huge task for Tottenham to win against Liverpool. Because they learnt a lot last year and that often leads to a situation you can capitalise on the next year.
“So I hope Tottenham come well prepared. They have to use their chances, especially at the beginning of the game. I think Tottenham can only win if they have a good start, if they are able to put pressure on Liverpool, get an early lead and play using counter-attacks.
“Then I see a chance for Tottenham. Apart from that I see Liverpool being the favourites.”
Spurs have come a long way in a short space of time under Pochettino, with Mertesacker having witnessed their progress from close quarters on the opposite side of a north London divide.He has been impressed by the development of Arsenal’s arch-rivals, adding on the impact of an Argentine coach: “I think it took some time, but Pochettino brought a new culture to the whole club. To all different areas.
“That took some time as I said, but the willingness to run, the clarity on how to play with the ball, which players are needed and which would best fit the club.
“That’s an ideal model, something you look at. Which players have been signed and how they have been integrated into the system. I think he has a very close connection to the players.
“They know it’s intensive and they can’t take shortcuts with this guy. That does not work.
“Even if I play I have to go to the training ground the next day and make some runs. It’s not a happy-go-lucky-culture, not a loose culture. He gets the best out of his players.
“He developed that in the recent years. That’s a culture based on work, combined with his great knowledge of the game.
“He gained that in the years when he played in Spain and France. There, he gained this appreciation for detail and his extensive football knowledge, not only the culture and the importance of having a hard-working group.
“It’s about what goals you want to reach on the football pitch. He brought consistency to Tottenham. He saw the team can take another step forward, the players can improve again.
“They've massively over-performed for years, especially when you see the budget they have. In contrast to Arsenal, to Liverpool, Manchester United, Manchester City, Chelsea. They have always over-performed with the budget they had. These performances are the most valuable.”