Obviously a very difficult choice here.
These players are universally known and are well, world's number one and two.
I will pick Nadal here. I watched some of his games and he seems to me to be back to his best which is a frightening proposition for any opponent.
To be a bit more technical in 2011 when Djokovic won his first Wimbledon he was vastly superior in this match-up beating Nadal 6 times in a row.
Things are however different now with Nadal winning 5 of the last 6 and this motivates this pick

Pick: Nadal
Odds: 1.73
Bookmaker: ➾ Pinnacle
Stake: 1 units
Tipster: Incontrol
TIPSTER: Incontrol | Total profit: +24.52 | Tips won: 29 |
Country: Romania | Total yield: +15.14% | Tips lost: 14 |
Speciality: Basketball | Total picks: 46 | Tips pushed: 3 |
04.01 | • Utah Jazz @ LA Lakers | 2 | 2 | ❌ | -2 |
23.10 | • Manchester United - Real Sociedad | 1.56 | 2 | ✅ | +1.12 |
22.10 | • Steaua Bucharest - Basel | 1.47 | 3 | ✅ | +1.41 |
22.10 | • Schalke - Chelsea | 1.4 | 4 | ✅ | +1.6 |
12.10 | • Chester - Cambridge United | 1.4 | 2 | ✅ | +0.4 |
11.10 | • England - Montenegro | 1.35 | 3 | ❌ | -3 |
05.10 | • Manchester City - Everton | 1.47 | 3 | ✅ | +1.41 |
01.10 | • Steaua - Chelsea | 1.83 | 7 | ✅ | +5.81 |
01.10 | • Steaua - Chelsea | 2.59 | 2 | ✅ | +3.18 |
01.10 | • Champions League Tuesday | 2 | 3 | ✅ | +3 |