De Gea has been in sensational form for a number of months now and he is widely regarded to be one of the finest goalkeepers in the world alongside Manuel Neuer.
The 25-year-old was close to a move to Real Madrid this summer but the deal fell through due to late paperwork.
Herrera believes it is a “blessing” for Man United that De Gea ended up staying at Old Trafford.
“He’s a genius. Purely on talent, I’ve never seen someone like him and we are lucky to have him,” Herrera said.
“The talent he has, very few have it in the world and David is one of them. It’s a blessing to have him close, and hopefully it will be for a long time.”
De Gea has played a huge part in United’s run of clean sheets in recent weeks and the team’s defence looks practically impenetrable with him and the likes of Chris Smalling at the back. There have been rumours that Madrid will go back in for De Gea next summer but the hope is that the player will change his mind about leaving over the course of the campaign.