In chronological order:
1. Djokovic def. Nadal - AO - 5–7, 6–4, 6–2, 6–7, 7–5
A brutal match that cemented Nole's greatness and gave him the chance for a non-CY Grand Slam. Played some phenomenal tennis during the second and third sets but ultimately won the match via determination, durability and a bit of luck.
2. Isner def. Djokovic - IW - 6-7, 6-3, 6-7
Lost another two tie breaks in a big match and an early indication that Nole 2.0 had regressed into Nole 1.5 territory.
3. Nadal def. Djokovic - RG - 4–6, 3–6, 6–2, 5–7
As above, really. Nole's level dropped enough that Rafa won three in a row in clay finals, most importantly at the final of RG of course. Still showed glimpses of supreme tennis - absolutely bossing the fourth set.
4. Murray def. Djokovic - USO - 6–7, 5–7, 6–2, 6–3, 2–6
Another crucial tiebreak loss that set the tone for the first half of the final. Disappointing to see his usually great stamina/fitness let him down a bit in the final set and also disappointed by how long it took him to adapt to the dreadful conditions.
5. Djokovic def. Federer - WTF - 7-6, 7-5
Highly entertaining match of great quality with Nole reinforcing that he's still the best player around by some distance even if he didn't bring his A game at some important moments during the year.
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Choosing 3 losses feels weird
But it was an odd year for Nole imo.