Hall of Fame
Fedr playing Djokr twice this year by default drops some of his ace counts. Plus, he served a little better in 2018, I think. As for tourneys played, he played one more in 2019.Interesting to see how low 2015 is considering how renowned his serving was that year. I'd be interested to do the math and how many it is per match for each season.
The huge drop from 2018 to 2019 is also really odd since I'm pretty sure he played more matches this year. He added in 3 clay tournaments and skipped Stuttgart, so it should be at least 2 more tournys.
Edit: I just glanced through his year-by-year stats and it looks like 2019 was the highest 1st serve % he's ever had (only 1%, but still). So maybe he was serving safer and not going for as many aces this year? I didn't really notice throughout the year if he wasn't going for the lines as much.
2018: HC, AO, Rotterdam, IW, MIA, Stuttgart, Halle, WB, Cinci, USO, LC, Shanghai, Basel, Bercy, WTF, (15 total)
2019: HC, AO, Dubai, IW, MIA, Madrid, Rome, RG, Halle, WB, Cinci, USO, LC, Shanghai, Basel, WTF (16 total)