Aleksandar Kolarov is "one step" away from joining Roma after seven years with Manchester City, manager Pep Guardiola has confirmed.

The Serbia international did not feature in City's opening pre-season fixture on Thursday, a 2-0 defeat to rivals Manchester United in the International Champions Cup, with midfielder Fernandinho and out-of-favour central defender Eliaquim Mangala filling the left-back berth between them.

Kolarov was the only senior full-back to remain on City's books at the end of last season, with Pablo Zabaleta, Gael Clichy and Bacary Sagna all released when their contracts expired.

England right-back Kyle Walker has arrived for an initial fee of £45million from Tottenham, and deals for Monaco left-back Benjamin Mendy and Real Madrid's Danilo are believed to be in the works.

Nevertheless, Guardiola felt unable to select Kolarov against United after the 31-year-old former Lazio man informed him of his intention to leave – although the boss insisted there are no hard feelings between the pair.

"We don't have another option, we don't have full-backs," Guardiola said when discussing his selections at a post-match news conference.

"We try to buy full-backs on the right side, not just Kyle because the other three full-backs, we didn't extend the contracts.

"I don't like to work with people who don't want to stay. Kola helped me a lot last season in terms of many, many things.

"But he had a big chance to go back to Rome where he was before and he spoke to me, the club and asked me to leave.

"I don't like to stay with players who don't want to stay. That's why it's the best option for everybody.

"I wish him all the best because he's a really nice guy. We had an excellent relationship. I was very pleased to train him and I wish him and his family the best."

United scored a pair of quickfire goals late in the first half through Romelu Lukaku and Marcus Rashford in Houston, with City goalkeeper Ederson's role in the Belgium striker's opener coming under the microscope.

However, there were more encouraging signs from another debutant, with Guardiola struggling for superlatives with which to praise 17-year-old youth team midfielder Phil Foden.

"You [the media, fans] are the lucky guys who saw the first game, for the first team for Manchester City, of this guy.

"It's a long time since I saw something like this. His performance was another level. He's 17 years old, he's a City player, he grew up in the academy, he loves the club, he's a City fan and for us he's a gift.

"He will stay with us, training with us in the pre-season and maybe he'll stay with us in season because he's special."