The Nerazzurri boss insists that not only did the Colombian midfielder not want to leave - despite links with Inter and Barcelona - he also wanted to hold onto him
The Colombia international looked set to join Valencia on deadline day but the proposed deal collapsed, while there were also reports that the player's representatives also turned up in Barcelona hoping to persuade the Catalan club to sign the 28-year-old.
However, Mazzarri says that, not only did Guarin not want to leave, he did not want the midfielder to go either.
"He’s always wanted to stay at Inter and he was on the market because of management choices," the Nerazzurri boss told his club's official website.
"However, I’m convinced he's very happy to have remained here and we're very happy to have him."
Inter were reportedly looking to offload Guarin to raise funds for bids for Paris Saint-Germain winger Ezequiel Lavezzi and Liverpool attacker Fabio Borini.
It is now being reported that those moves have merely been put on hold until the January transfer window but Mazzarri would only say: "That's a question for the directors.
"The transfer market is closed. [On Thursday] we're going to start training again and we're not going to think about transfers. We'll focus on games."