The newspaper says Spurs chairman Daniel Levy was willing to sanction the deal but boss Mauricio Pochettino has turned down the opportunity to sign the South American attacker.
"We don't want to think about it", Son added.
'Maybe I'm boring, because I always answer the same way - of course they are both very good sides, like us.
He said: "We cannot put the excuse that we are not a real contender but we are going to try, we are going to dream because we are close, we are there in a very good position and we are going to try and fight until the end to be as high as we can".
Pochettino declined to comment on reports that he had been keen to sign the striker Michy Batshuyai, who ended up joining Crystal Palace on loan from Chelsea on Thursday.
Harry Kane, who Janssen was bought to be cover for, is still out of action, but Pochettino is pleased with the striker's recovery from injury so far.
Tottenham did not sign a single player in the summer and go into the final day of this month's transfer window without making any additions.
"Before it was so clear because he wanted to leave and of course he wasn't in our plans", Pochettino added. "Now when you cannot achieve what you want, it's important for him to feel again he can be helpful".
"He is a person and not a chair, or a sofa, or furniture, and he will be involved with the first team and try to do his best, and try to get fit and be competitive".
Deadline Day has been and gone and now we can get back to focusing on the important stuff, winning Premier League games.
"For different reasons he can't go away - reasons that are hard to understand for me. We care and my decision was to open the door and invite him in again and be like another player here".