There are many great rivalries and match ups on the ATP Tour, so it's hard to only pick out three.
The match ups that I have chosen are personal favourites of mine (from the Big 3) and who I feel have really exciting tactical battles when they play (e.g. bringing the best out of each other).
1: Rafael Nadal vs Dominic Thiem
Nadal and Thiem have had many amazing battles on court in the last few years. The more they play the better it gets and they are starting to understand each others playing styles to perfection.
Rafa leads the H2H 9-5, however it is 3-3 in their last six meetings with Dominic getting the last win at the Australian Open this year.
This is always an interesting match up as Dominic is the only player that can cause Rafa trouble on clay; apart from Djokovic (although I would argue Dominic is still tougher for Rafa on this surface). Thiem has consistently been able to beat Rafa on clay at least once each year for the last four years (2016-2019), proving a tough obstacle for Rafa in going for more clay court titles.
Thiem has even shown he can overpower Rafa in recent years and put him in defensive/uncomfortable areas on the court. The question moving forward will be if can he do it in a Masters 1000 or Grand slam final. So far Rafa has come out on top in these finals and brought his best level of tennis. Watching these two play you won't see more power, intensity and heavy spin anywhere else.
2: Novak Djokovic vs Stan Wawrinka
When these two step out on court they always seem to bring the best out of each other and have the ability to play their best tennis. They have competed in many extraordinary battles, including; Australian Open 2013 where Novak won 13-11 in the 5th set, the 9-7 match in 2014, not to mention ANOTHER five setter in 2016 AO semi-finals. Then for Wawrinka, he beat Novak at the French Open 2015 final and US Open 2016 final both in 4 sets. It's pretty impressive winning your first French and US Open title against the world number one.
Despite Novak leading the H2H battle Wawrinka has proven he can be the better player in most previous matches. Stan has shown he can consistently overpower Novak for the duration of a match and make Novak feel out of rhythm on court. Novak fans would agree that Stan at his best is more of a threat than any other player on tour.
Stan has incredible power but also the ability to chip short balls from defensive positions which doesn't suit Novak's game. He quite often 'bunts' his returns which then forces Novak to attack on the first shot. Novak often tries to hit through Stan by hitting flat, powerful groundstrokes but this has not worked. "The better I play, the better he plays" is a definite true quote here. Roger is able to rush Stan off his game and change the pace, while Rafa also can do this by lefty cross court spin and higher balls making Wawrinka playing out of his sweet spot, but Novak's game doesn't allow this.
3: Roger Federer v Juan Martin Del Potro
In my opinion this rivalry is extremely underrated. The last 12 matches they have played (2012-2018) there has only been ONE match that has NOT gone to the final set. Delpo has won 5 out of these last 12 matches, surprisingly including the last 3 finals in a row. The raw power, talent and serving between these two greats is always exciting. There is always a great mix between short points and long rallies so fans get the best of both worlds.
The first match that most people will remember is when Delpo beat Roger in the US Open 2009 final in 5 sets which was his first and only grand slam. Ever since this win in 09', it has spiraled the best out of them both and every match they play is extremely close with lots of tiebreaks and final sets. I really enjoy how well Delpo can battle with Roger from the back of the court, especially from his forehand side and with his big serve it allows for an even match up. Hopefully we will see these two champions step out on the court against each other again in the near future...