Pep Guardiola fired a warning to Manchester City's rivals after the club's first match of a pre-season tour of Japan on Sunday, declaring star striker Erling Haaland was in "much better" shape than last season.

Haaland claimed a brace after coming on at half-time to help City roar back from two goals down and beat J-League champions Yokohama F-Marinos 5-3 in Tokyo.

The Norwegian struck 52 times in his debut season at City, including a single-season Premier League record of 36 goals.

"Comparing last season in that period he's fitter, much better than last season when he arrived," Guardiola told reporters after the Tokyo match.

"Of course (he) looks good but (he) is still a way from the best condition, like everyone."

As impressive as Haaland was in driving City towards their historic treble of Premier League, FA Cup, and Champions League, however, the goals dried up for him at the end of the campaign.

The striker, who turned 23 on Friday, failed to find the net for City in his last five appearances -- the longest scoreless streak since he joined the club.

With that in mind, Guardiola noted that it was "important for him to score the two goals in the first game" in Japan.

"We know him. In a few weeks he will be in even better condition than now," said Guardiola.

John Stones, Julian Alvarez and Rodri were also on target for Guardiola's side in their first outing since defeating Inter Milan 1-0 in the Champions League final last month.

Only four of the players who started that game were in the initial City XI against Marinos in Tokyo, with captain Ilkay Gundogan having left the club for Barcelona.

Haaland, Rodri, Ruben Dias, and Bernardo Silva all made appearances in the second half though, and Guardiola also had a positive update concerning influential midfielder Kevin De Bruyne.

The Belgian was forced off injured in the Champions League final, but Guardiola revealed that the he was feeling "much, much, much better".

"I don't know about Bayern Munich or the next game, Atletico Madrid, because of course he has to train. But he is so close. He's coming back soon," said Guardiola.

City will next play Bayern on Wednesday in Tokyo. They then travel to Seoul to take on Atletico.