Rafael Nadal has warned Juan Martin del Potro he is playing better and better with every match that goes by.
The two of them are about to clash at the US Open semi-final, and Nadal will be eager to avenge his defeat in 2009, when he was eliminated by the Argentine at the same stage.
The Spaniard enjoyed a relatively slow start at Flushing Meadows, looking a shadow of his best.
He was not really convincing in the first three rounds, where he defeated relatively weaker opponents, doing just about enough to advance through.
But, in the second week of the tournament, he has picked up the pace.
An oustanding win over Alexandr Dolgopolov was followed by an even more convincing victory over Russian teenager Andrey Rublev in the quarter-finals.
Nadal gave his last two opponents a combined 12 games, as he began to justify his number one place in the ranking.
The improvement is obvious and appreciated by fans and specialists. Still, Nadal believes he needs to and will be on an even higher level against Del Potro in the semis.
"I think I have been improving during the whole event, and I have been doing step forward match by match, and now is the moment to do it, another step forward, a little bit higher is possible, too.
"So I think I have the attitude to try to make that happen. I am excited about that semi-finals. I know I gonna have a very tough opponent in front. And I need to play my best.
"So since tomorrow morning, because today I’m going to enjoy the few hours off that I have, enjoy the fact that I am in semi-finals. But I wake up tomorrow morning knowing that I have to do something more, and I’m going to work hard to work in that way."
Rafael Nadal holds a positive 8-5 record against Juan Martin del Potro, but has been defeated the last two times they met.
In addition, Del Potro won their only clash at US Open back in 2009, when at the same stage he came victorious and eventually lifted the trophy.