Former Hong Kong champion Werther has been officially retired with hopes of a comeback in New Zealand thwarted by injury.

After finishing second in the 2015 Queensland Derby for New Zealand trainer Andrew Campbell, Werther was sold to Hong Kong and sent to the John Moore stable.

Werther won six races in Hong Kong for Moore, including the Hong Kong Derby (2000m) and three others at Group One level.

The injury-plagued gelding last raced when third in the Group Two Jockey Club Cup (2000) at Sha Tin in November, 2018.

He returned to Campbell in New Zealand to recuperate from a suspensory injury and the hope of a return to the track.

Although the signs were encouraging about a race return, the ultimate decision to retire him was easy.

"I galloped him on Saturday and I was going to trial him today (Tuesday) but I wasn't quite happy with his leg," Campbell told NZ Racing Desk.

"There was a slight reoccurrence of his injury. I talked to his owner and we didn't want to risk him.

"He has been a fantastic horse.

"Even when we sold him we got a great thrill watching him race in Hong Kong. It has been a hell of a ride.

"He will get the best of treatment and we will get him the nicest home. He is a grouse horse so we will do the right thing by him for sure."