He has some rare blood disease that often affected him, and I also think the grind of trying to break Connors record of finishing the season number one 5 years in a row wore him down. He struggled over the line in 1998.
There’s another record we ought to put in context: Connors 5 in a row. Does anyone really believe that Jimmy was the best player in the world from 1974-78?
The point system was wonky back then. As you know, Connors played and won a lot of very low level tournaments that probably would be closer to today's Challengers. His #1 ranking in 1974 was indisputable, but after that it gets dicey - Ashe and Borg were close in 75. Connors is probably the clear #1 in '76 again, but then it is well-known that Vilas probably got robbed in '77 (though he, too, piled up a lot of weak low-level titles). Borg and Connors were very close in '78, though I think we see the passing of the generational torch. Borg was the well deserving #1 in 79 and 80 and Mac in '81, but 82-83 are close. Some argue that two-Slam-winning Connors probably deserved #1 in '82.
On the other hand, Connors is sometimes a bit under-appreciated. He almost single-handedly ushered in the new era in '74, demolishing Rosewall and reigning over the Ashe/Newcombe/Nastase/Smith group. He was also right there with Borg, and then Borg and McEnroe, and remained an elite player into the mid-80s, and relevant for a few more years after. He and Lendl both tend to get de-emphasized when talking about ATGs, but I think they're more in the group of Borg/Sampras/McEnroe than they are with Agassi/Becker/Edberg/Wilander.
But the 90’s weren’t as Wild West as tennis in the 80’s. That was a really hyper competitive decade. Often ugly and nasty too. Look how many great players there were, battling for the top. I don’t know how many Number Ones there were in the 80’s but I’d hazard a guess that all of them were bona fide great players.
I can answer that question! The 90s started with Lendl still reigning, but Edberg took over later in the year and was #1 for most of 1991, except for a couple brief coups by Becker. It was Edberg to start '92, but then Courier took over (though Edberg wrestled it back a couple times). Finally, Pete took over in '93, but Courier grabbed it back later in the year for a short time. It was all Pete in '94 and less than half of '95, with Agassi probably at his best, but Pete took it back to finish the year.
In '96, it was mostly Sampras, but Agassi and Thomas Muster had short stays. '97 all Pete, and '98 mostly Pete except for a couple brief reigns by Marcelo Rios. By '99 it was really breaking up: Pete started and would win it back several times, but you also had Carlos Moya, Yevgeny Kafelnikov, Patrick Rafter and twice--including ending the year--Andre Agassi.
So in the 90s we have, in order: Lendl, Edberg, Becker, Courier, Sampras, Agassi, Muster, Rios, Moya, Kafelnikov, Rafter. 11 players.
It would remain mixed for the first few years of the 2000s: Agassi, Sampras, Safin, Kuerten, Hewitt, Ferrero, and Roddick all were #1 in the first four years. From 2004 on, you have a bit of Roddick, but then it is all Roger, Rafa, and Novak. Similarly with the 2010s, until Andy joins the gang in 2016. And in the 2020s, it started with Rafa, but has mostly been Novak, with a bit of Medvedev and Alcaraz (and presumably a lot more Alcaraz to come and, I would guess, Rune at some point - possibly more Medvedev and maybe Sinner, too).
The 90’s was largely dominated by Pete, but Agassi was obviously a factor, Becker rose and fell periodically, Edberg, Rafter, some weird stylists like Fabrice Santoro, who was two handed in both sides and something of a pesty magician with the ball and racket. Kuerten, and a bunch of great dirtballers who could keep you tied up in on clay court litigation for days. Big ballsy grasscourters. It really was a tale of two cities. Clay and grass were further apart than ever. Some players never seen each other between the two hard court phases. Some would be gone home early on the clay, some would totally skip the grass. A lot of overrated players too, which is natural.
It was way more open, except Pete was always there once he found his range. Cool, imperturbable, economic and accurate in his shot making. Agassi was the anti-Pete in more than just tennis. An hysteric, occasional cheat, fashion victim. I suppose where Pete really suffered in the press is that he wasn’t iconic in any way. Look at photos of Borg in his playing days and he still looks like a mysterious king, aloof and practiced, above the fray somewhat, never suffering from the indignity of breathlessness or sweat.
Look at Pete and you’ll wonder why his tongue is sticking out…
One thing I was surprised about when I started researching with Elo is that the "weak era" -- if we go by Elo - actually started earlier in the 90s than I thought. This
might be because the competition was more tightly packed together, so that players were essentially equalizing each other. Pete's Elo was always suppressed by his weak performance on clay (his overall peak Elo is 2407 -- lower than Becker and Vilas, but his non-clay peak Elos are over 2500).
From the late 70s to the early 90s, there has a lot of elite talent: Connors, Vilas, Borg, McEnroe, Lendl, Wilander, Edberg, Becker, and then Agassi, Courier and Sampras, all with overlapping peaks, and no real gaps in which there weren't at least 2 or 3 ATGs in peak form. After Lendl faded, and Edberg not long after, plus Courier's brief time at the top, you had fewer all-time greats in peak form. Sampras was consistent until 98-99ish, but Agassi and Becker were both up and down, and Becker was basically finished as an elite after '96. And then Sampras started teetering in '98, fully opening the door for the "Wild West" of the 99-03 era.
Or to put it another way, among players who didn't win 6+ Slams, here are the players who won Slams in each decade:
1980s: Teacher, Kriek (2), Noah, Cash, Chang
1990s: Gomez, Stich, Courier (4), Bruguera (2), Muster, Kafelnikov (2), Krajicek, Rafter (2), Kuerten, Korda, Moya
Obviously a lot more 1-4 Slam winners in the 90s implying more distributing and/or less high end talent. And it is worth noting that in the 80s, two of those Slam winners only won at the very weak AO in 1980-82, when it more like an ATP 500 in terms of depth of talent.