Chadwick emphasizes the importance of understanding the personalities of both brands. "If a sports club is big, loud, ostentatious and successful, then there will be problems if the entertainer's characteristics appear to be at odds with the club's."

Earlier this month, Lu Han, once dubbed the "Chinese Justin Bieber", was named as a "Red Devil Messenger" by Manchester United.

His passion for the Reds is well documented by the fact he holds a Guinness World Record for the most comments on a Weibo post. His "Ten years a fan, Lifelong a Red Devil!" post in September 2015 broke his own record, and has received more than 100 million comments to date.

United is the one of the most popular sports teams in China, and was named as the number one club online in 2017 and 2018, but dropped to the third after Real Madrid and FC Bayern Munich in this year's Red Card Report by the Mailman Group.

In the fast-paced digital era, United is keen to bolster its popularity in China by teaming up with influential key opinion leaders. Lu, who has Weibo followers of more than 59 million, came as a natural choice.

The ongoing convergence of sport and entertainment brands is likely to intensify rather than abate, critics say, but argue that it is debatable whether this is a sustainable approach, and say marketers should be aware of who contributes most to their revenues.

"Is it those who want stars, celebrities and entertainment from their sports, or is it those who buy tickets to a game and want to stand on the terraces watching their favourite team?" Chadwick said. "Sports should be careful not to alienate their core customers as they pursue perceived lucrative new revenue streams."