The Togo international has been training away from the first team after returning from compassionate leave on Monday.
With the striker's days appearing to be numbered at White Hart Lane, Defoe believes his absence from first-team affairs is damaging.
"I don't think it helps the team, to be honest," he told Sky Sports News.
"Someone like Mani, he's a great player and has played for some of the top clubs in the world and is someone that we're going to need. We will need his goals and what he brings to the team.
"He's keeping himself fit, he's a happy guy, he loves his football, and hopefully he'll be back soon with the team."
Defoe is yet to start a Premier League game under Andre Villas-Boas this season, with Roberto Soldado the preferred option so far.
The England international believes he needs to play more regularly if he is to secure a place in Roy Hodgson's squad for the World Cup.
"In a World Cup year you have got to play, it's as simple as that," he continued.
"To get into any England squad, it's based on merit. So you have got to play, I understand that. I also understand that it's a long season, there are so many games to go and a lot of football to be played.
"I just have to try and keep myself sharp and fit."
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