The 23-year-old stepped up last season after being recalled from a loan spell with Grasshoppers in January.
"He's been excellent since he's come in, absolutely excellent," Coady told the Express & Star.
"Our defence is something we have built ourselves on in recent years.
"It's something we need to improve, set pieces and goals, and it's something we look at as a defence. But Toti has been fantastic since he's come in. He was on holiday in January, so to get the call to come in and then play as he has in the Premier League, is fantastic.
"He's a cracking lad and he's been improving every day."