With Arsenal breaking their record transfer fee to bring in Mesut Ozil from Real Madrid on Monday, Wenger was also keen to sign Ba on a temporary deal before the deadline.
However, Mourinho put a stop to the proposed switch because he felt it would further strengthen the Emirates Stadium outfit's hopes of winning the Premier League.
"We didn’t accept Arsenal’s offer for Demba Ba because the signing of Ozil makes them title contenders," said the Portuguese.
Mourinho bought Ozil from Werder Bremen during his time at the Santiago Bernabeu and believes the "unique" Germany playmaker is one of a kind.
"There is no copy of him - not even a bad one," he added.
"He is the best number 10 in the world. He makes things very easy for me and for his team-mates with his football vision and the decisions he makes.
"Everyone loves him and sees a bit of Luis Figo and Zinedine Zidane in him."
