Manchester City got the better of Premier League title rivals Arsenal, thanks to Nathan Ake's second-half goal that secured a 1-0 win at the Etihad Stadium in Friday's heavyweight FA Cup fourth round tie.
In a game of few clear-cut chances, Ake's second goal of the season broke the deadlock in the 64th minute after substitute Julian Alvarez's shot had struck the post.
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As City move onto the competition's last 16 for the eighth consecutive season, Arsenal are left to focus on their challenge for a first Premier League title in 19 years. Mikel Arteta's side have a five point lead over City and a game in hand, with the two teams to meet again in the league on Feb. 15.
City will go into that game having beaten Arsenal in their last six meetings in all competitions.
"Tight game, second half was better," Guardiola told ITV Sport. "Really difficult opponent.
"There is not one person in the locker room that is not very happy for him [Ake]. We are happy for the goal and how he controlled one of the most dangerous players in the Premier League now in [Bukayo] Saka.
"As a manager you want players like Nathan. He deserves all the good things in life."
While Pep Guardiola made just two changes to his City lineup -- Stefan Ortega replacing Ederson in goal and Ake in for Aymeric Laporte at the back -- Arteta refreshed his team with six alterations to the side that beat Manchester United on Sunday.
As well as a start for United States international Matt Turner in goal and Kieran Tierney replacing former Man City left-back Oleksandr Zinchenko, there was a first Arsenal start for January signing Leandro Trossard.
Despite changing more than half their team, it was Arsenal that had the better of the opening 45 minutes. And Trossard was at the heart of all his side's best moves going forward.
After just five minutes, his fine work down the left led to a shot from the on-rushing Takehiro Tomiyasu that forced a diving save from Ortega. The City backup was called into action again later in the half, this time when Trossard went for goal himself with a powerful left-footed drive that was turned away one-handed.
Arguably the best opportunity, though, came when Eddie Nketiah failed to continue his impressive goal-scoring form as he volleyed Torssard's cross wide from six yards.
At the other end, City's only real threat came from direct balls to Haaland. Turner was alert off his line to prevent the prolific frontman from getting on the end of a ball following an error from Rob Holding, while a later lobbed effort went wide of the target.
As the second half got going, though, City began to crank up the pressure. And a double substitution just before the hour mark proved decisive in breaking the deadlock.
Just minutes after arriving on the pitch, World Cup winner Alvarez turned and unleashed a shot from 25 yards that bounced back off the foot of the post. Jack Grealish did well to pick up the rebound and hold off defenders before laying the ball off to Ake, who finished neatly past Turner and into the far corner with his weaker right foot.
Arsenal almost responded immediately but Laporte, who replaced the injured John Stones in the first half, made a sensational last-ditch intervention to prevent a wonderfully inviting cross from Granit Xhaka reaching Nketiah for a close-range finish.
The visitors again came on strong in the closing minutes as they pushed for an equaliser that would have forced a replay but City's defence -- and Ortega in goal, in particular -- were equal to the challenge.
"I think we could have got much more out of the game," said Arteta. "One action changed it all.
"It is really difficult to win against this team but we went head to head with them. In the big moments, in big matches you have to make the difference. That is how you win these games."
Information from Reuters was used in this report.