Rafael Nadal has suffered two defeats in his first two singles matches of the season, but says he feels like he is improving all the time.The Spaniard is the Australian Open defending champion but struggled with injuries throughout last year which cut his 2022 tennis season short. Back down under for the first time since he lifted his second Australian Open title, the 22-time Grand Slam champion has been competing for Spain in the inaugural United Cup team event.In the first match, Nadal was beaten by British number one Cameron Norrie in three sets. Australia’s Alex de Minaur then defeated the world number two in his second singles match, again in …