The exciting winger will make his City debut in Saturday's third-round tie against Exeter after his transfer from Bournemouth was confirmed on Friday, with the clubs striking a deal worth an initial Stg 62.5million ($A125.5 million).
With City facing a number of injury problems, Guardiola has confirmed the Ghana international will go straight into his squad to face the League One (third-tier) side at the Etihad Stadium.
"I don't know if he will start but he will be selected for sure because we don't have too many players," Guardiola said at a press conference.
With attackers Savinho and Oscar Bobb among the injury casualties and forward Omar Marmoush at the Africa Cup of Nations, Semenyo could have an immediate opportunity to make a mark in the side.
The 26-year-old impressed for the Cherries in the first half of the season, scoring 10 goals and providing three assists in the Premier League.
Guardiola said: "Everybody knows the qualities. He played extraordinary at Bournemouth and he can play on both sides, right and left, and he can play as a striker as well, with his pace.
"Many clubs wanted him and he decided to join us - so all I can say is thanks to him.
"We followed him for a long time and in the end, with the situation we have up front and with the wingers, we needed to reinforce for the next years and that's why the club made the effort to take him.
"He is the perfect age at 26 with the best years to come."
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