Brendan Rodgers' side missed the chance to go top of the Premier League on Saturday as goals from Santi Cazorla and Aaron Ramsey extenders Arsenal's advantage at the summit.
The game marked Coutinho's return from a shoulder injury as he was introduced at the interval and Toure is confident that, with the Brazilian's help, Liverpool will return to winning ways.
"In the first half we couldn't keep the ball well enough and we spent too much energy running after it, but in the second half when Coutinho came on the game changed," he told the Liverpool Echo.
"We were much better and created some chances but we couldn't take them.
"I call Coutinho 'my player'. I think he's amazing and can make the difference in matches.
"This season he's been out injured but now he's back he's going to be amazing for us.
"I really like him. He's my best player. In training he's one of the hardest to mark. He's still young but he's got that magic."
Liverpool, who are now five points off top spot, host Fulham on Saturday, while their next away trip takes them to rivals Everton on November 23.
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