Floyd Mayweather Jr returned to the ring for the first time in 21 months with a unanimous points victory over Juan Manuel Marquez in Las Vegas.Mayweather, who announced his retirement after beating Ricky Hatton in 2007, dominated triple world lightweight champion Marquez of Mexico.The American knocked down Marquez in the second round, then peppered him with damaging shots to remain unbeaten.Marquez stepped up two weight classes for the non-title welterweight fight.And that step up told as Mayweather dominated all 12 rounds against his smaller opponent with his left jab and agile movement, improving his career record to 40-0 with 25 knockouts.Mayweather, who held a significant weight and reach advantage over five-time world champion Marquez, was a heavy favourite going into the bout at the MGM Grand Garden Arena and knocked down Marquez in the second round.The 32-year-old showed no signs of rust after his lengthy stint away and controlled the pace of the fight with his lightning hand and foot speed, rock-solid defence and a series of telling combinations.Marquez had a bloody nose by the midway point of the bout, and Mayweather landed several hard shots late in the sixth.Whenever Marquez appeared to land a combination, Mayweather backed away with a grin."I've been off for almost two years but it felt really good to be back," Mayweather said in a ringside interview. "I was happy with the victory but I know I can get better."That guy is tough as nails," added Mayweather, who gained one-sided verdicts from all three judges - by 118-109, 120-107 and 119-108."He was a great little big man. I threw a hell of a shot that dropped him, and then he got back up and kept fighting. He's a tough guy."Marquez, who had never fought above 135 pounds, said: "He surprised me with the knockdown."He hurt me in that round but not at any other time."I don't want to make excuses but the weight was the problem," added the Mexican, who was four pounds lighter at Friday's weigh-in."He's too fast. When I hit him he laughed but I knew he felt my punches. I did the best I could do."Eighteen months ago, Marquez lost a narrow decision to Manny Pacquiao - who is believed to be Mayweather's first choice for his next bout.The prospect of a Mayweather-Pacquiao fight would be hugely appealing, but another potential opponent has already stepped forward.Sugar Shane Mosley demanded the attention of Mayweather in the ring immediately after the fight, with officials forced to separate the two.Mayweather did not comment on a fight with Mosley, but his uncle and trainer, Roger Mayweather, earlier said Mosley would produce "a better fight than Pacquiao".Source: BBC