The Mexican international, also known as Chicharito, has found starts hard to come by this season, and has even admitted that he was looking for a move away from the London Stadium during the January transfer window.
He did, however, come off the bench to score West Ham's equaliser in their 1-1 draw at Stamford Bridge on Sunday, and Redknapp was quick to commend the impact of the striker.
"He does a great job holding the ball up for his team, being aggressive and holding off Gary Cahill. It's a good piece of play. He's one of the best finishers in the game," Redknapp told Sky Sports.
"He is up there with the best and it's a brilliant finish, it's unstoppable. Great forwards seem to have that extra bit of time."
Manager David Moyes has opted to start Marko Arnautovic as a lone striker in recent weeks while using Hernandez as an impact substitute, and Redknapp believes that this has contributed to the Hammers' upturn in form.
"He's almost stumbled across it but playing Marko Arnautovic as the striker has really helped West Ham. He's more mobile, he gets hold of the ball, he can do something with it and even the penalty appeal, that's him at his best.
"But when you have 70 minutes and you need someone to come on - an assassin, a goalscorer - that's what Hernandez brings. He's one of the best in the business."
Former West Ham manager Slavan Bilic also agreed with Redknapp's assessment of the striker.
"He's a natural goalscorer and he's there where he has to be. He's not dangerous outside the box or around the box, but in the box, he's the best finisher. Everything he thinks about is being in the box to come for a second ball,"