With Cristiano Ronaldo's future as uncertain as it has ever been, Manchester United and Chelsea are set to battle it out yet again in the transfer market. According to a report published by the Athletic, the Blues have not ruled out a bid for the Portuguese superstar and could pull off one of the signings of the summer.Manchester United failed to qualify for the UEFA Champions League this year and are in the midst of a transitional phase at the moment. Erik ten Hag has been appointed as the manager of the club and is currently overseeing the Red Devils' plans in the transfer market.B/R Football@brfootballChelsea are interested in signing Cristiano Ronaldo and have held talks with his agent Jorge Mendes, reports @David_Ornstein8933676Chelsea are interested in signing Cristiano Ronaldo and have held talks with his agent Jorge Mendes, reports @David_Ornstein https://t.co/rRJBL3bu7cCristiano Ronaldo has turned 37 years of age this year, however, and is unlikely to wait for Manchester United to hit their stride again. The former Real Madrid star has never played in the UEFA Europa League and is reportedly seeking a move to a club that has qualified for the Champions League.Chelsea are also in need of a few reinforcements this year and will need to move quickly to replenish their squad. The London giants are in the market for a striker and could bolster their title credentials by bringing Cristiano Ronaldo to the club.Chelsea emerge as potential destination for Manchester United's Cristiano RonaldoCristiano Ronaldo has been impressive in the Premier LeagueWith Romelu Lukaku on his way to Inter Milan, Chelsea are in dire need of some firepower in the final third. While the Belgian striker failed to meet expectations yet again at the club, the Blues will need to find another hitman to lead their line.Manchester United remain insistent that their Portuguese talisman remains contracted at the club until 2023 and is not for sale. The 37-year-old striker did not attend training this week, however, and has cast further doubt on his future at the club.Fabrizio Romano@FabrizioRomanoConfirmed. Cristiano Ronaldo to miss return to Manchester United training today “due to family reasons”, club have accepted this explanation. #MUFCMan United are aware of his desire to leave the club - but insist on their position: not for sale, want to keep him.620345489Confirmed. Cristiano Ronaldo to miss return to Manchester United training today “due to family reasons”, club have accepted this explanation. 🚨🇵🇹 #MUFCMan United are aware of his desire to leave the club - but insist on their position: not for sale, want to keep him. https://t.co/Tzj40IidtUThomas Tuchel led the London outfit to a third-place finish in the Premier League this year. Chelsea are currently facing a few financial hurdles at the moment, however, and will need to dig deep into their resource pool to pull off a transfer for one of the world's most high-profile players.Manchester United have expressed interest in several players so far but will need to go the extra mile to keep their players. Cristiano Ronaldo scored 24 goals for the Red Devils last season and remains one of the club's most important players.