Former F1 boss Bernie Ecclestone believes Lewis Hamilton is "fed up" with Formula One and as a result is "not the racer he was" in the past.
Reigning world champion Hamilton is still yet to win a race in 2018 and found himself out of form at the Chinese Grand Prix, where he finished behind teammate Valtteri Bottas in qualifying and the race. Although Hamilton confessed he never felt 100 percent throughout that weekend he came to Baku, host of this weekend's Azerbaijan Grand Prix, confident of a quick fix.
Ecclestone, who was removed from power at the start of 2017, says he has noticed a change in Hamilton's demeanour in recent months.
"He doesn't seem to be the Lewis that he was before," Ecclestone told Sky Sports on Friday. "I don't know whether it's me, but when you talk to him and see him act the way he acts generally, he's not the racer he was.
"He's still very quick, still super talented, still a super nice guy. But maybe he just getting a little bit tired of travelling and he's fed up with things.
"I thought Lewis would win every race, so I've been proved wrong. It would be nice to see Sebastian [Vettel] win because he's a mate of mine and I support him always. So I hope he can get the job done."
Hamilton is currently in the final year of his Mercedes contract and is yet to sign an extension beyond 2018. Both parties have frequently stated that a new deal is a matter of when, not if, although Hamilton recently suggested the next set of regulations being agreed by F1 bosses and teams might well influence his final decision.