'Chicarito' left United for Bayer Leverkusen in 2015 after spending five years at Old Trafford.
The 28-year old was part of a clear out by Louis Van Gaal and was subsequently sold to the Bundesliga club for £7.3million. Current boss Jose Mourinho has since denied that he would have ever completed the move had he been manager.
"Manchester United sold players that I would never sell and they bought players that I would never buy," Mourinho said.
"I would never have sold [Angel] Di Maria, Chicharito, Danny Welbeck. Never, no chance!"
Hernandez had a blinder in his first season at Leverkusen, netting 26 goals in all competitions, but has struggled to find consistency in the current campaign.