The international break provided some exciting moments, but international football cannot match the intensity and quality of club football.Top-quality players have once again displayed their class, producing some excellent performances since the season began. Some are still finding their feet, but should come good as the season progresses.There is surely more to come, and many new players will emerge this season with huge potential. Right now, though, the established stars have once more shown why they are revered across the world.On that note, here's a look at the five most in-form players in the world right now:#5 Cristiano Ronaldo (Manchester United)Manchester United vs Everton - Premier LeagueManchester United boss Ole Gunnar Solskjaer is once again under pressure after some poor recent performances and results.Despite boasting a star-studded squad, United look disjointed. One superstar who has done well is Cristiano Ronaldo, though. The 36-year old returned to Old Trafford this summer amid much fanfare, and he has not disappointed so far. Goals have flown freely from Ronaldo.ESPN FC@ESPNFCCristiano Ronaldo has been named Premier League Player of the Month for September 🏆3:47 AM · Oct 8, 2021244832018Cristiano Ronaldo has been named Premier League Player of the Month for September 🏆 https://t.co/LF6jQIHFrcThe Portugal international has scored five goals in six appearances for United thus far, including the winner against Villarreal in the Champions League. Ronaldo's performances saw him win the Premier League Player of the Month for September. On Saturday, he opened the scoring for Portugal against Qatar.#4 Robert Lewandowski (Bayern Munich)FC Barcelona vs Bayern München: Group E - UEFA Champions LeagueHis performances have been so consistent that no one is surprised nowadays whenever Robert Lewandowski breaks a goalscoring record.Regarded as one of the best strikers to have played the game, Lewandowski is only getting better with age. The 33-year-old scored 41 league goals last season to break the late Gerd Muller's record of most goals (40) scored in a Bundesliga campaign. This season he has already registered seven in the Bundesliga and four in the Champions League.ESPN FC@ESPNFCThe only player with 40+ goal contributions in the League and European competition in 2021.Lewandowski for the Ballon d'Or? 🤔5:32 AM · Oct 9, 2021156581496The only player with 40+ goal contributions in the League and European competition in 2021.Lewandowski for the Ballon d'Or? 🤔 https://t.co/prPuQygBvRLewandowski was the best player in the world when Bayern Munich won the treble in 2020. He is among the favourites to lift the Ballon d'Or award this year; the Poland international certainly deserves the recognition.You may also like: 10 most valuable players in the world - October 2021.