I am a 1400 rated player. We have 4 players in our club rated 2000+. If I sat down and played 100 games against one of them, I would lose 100 games. So, how does losing 100 games against one of these strong players EVER make me a better player? [sadly, none of them ever gives a post mortem].
It's partially who the opponent is, and partially how much better the opponent is.
I've gone from ~1750 to almost 1900 in the last year (approximate as ECF grades - 142-158 to those who understand ECF). In that time I've played a lot of players who are appreciably better than me. But not massively better; most have been 1850-2100. That meant I could still give them a challenge, even if I was stretched to hold them for the whole game. In fact a major moment in that improvement was I when I had to play my first ~2050+ player in that period, I was sort of doing OK but a little worse, and then I suddenly realised he a had let me off the hook. This 2050 player had made a mistake! I can not explain quite how much confidence that gave me, and I went on to draw the game, and in fact missed a win along the way. The whole episode set me up for the season, and the game is below.
So that's the first point, good enough so that you see and understand their plans, and that they stretch you, but also not so good that it's wham, bang, thank you mam. The second point is that a lot of the players I have played in this period have been kind enough to go through the games with me. This helped me understand their expectations, and often showed me ideas that I had not even considered. This was coupled with has the 2100+ player at my (small) club helping me, The later in particular clarified my impressions of my opponents plans, helped me identify some of my tactical weaknesses and showed me what both of us had missed over the board.
So for you I suspect 2000+ is a bit rich. But look for players who are
- Around 100-300 higher than you
- Are kind enough to spend at least a few minutes afterwards going through the games
- And then take the games to your trainer to check your opponent wasn't talking rubbish
Anyway here's the game that I referred to earlier. It's at move 19 I had my epiphany.
[Event "A Match in the League"]
[White "Ian Bush"]
[Black "Somebody Scary"]
1.e4 c5 2.d4 cxd4 3.c3 dxc3 4.Nxc3 e6 5.Nf3 Bc5 6.Bc4 Nc6 7.O-O a6 8.Qe2
( 8.e5 )
8...b5 9.Bb3 Nge7 10.e5 Ng6 11.Ne4 Be7 12.Nd6+ Bxd6 13.exd6 O-O 14.Bg5 f6
15.Bd2 Nge5 16.Rac1 Bb7 17.Nxe5 fxe5 18.f4?!
( 18.Bc2 )
18...exf4 19.Bxf4 Qh4
( 19...Nd4! )
( 20...Nd4! )
21.Rfd1 Qf5 22.Bc2 Qf6 23.Qh5 g6 24.Qc5 Rab8?!
( 24...Rac8! )
25.Bb3 Rfc8 26.Qe3 Rf8 27.Rc5 Rbc8 28.h4 Na5 29.Rxc8 Rxc8 30.Bxe6+ dxe6
31.d7 Rf8 32.d8=Q
( 32.Bg5! Nc4 33.Bxf6 Nxe3 34.d8=Q Rxd8 35.Rxd8+ )
32...Rxd8 33.Rxd8+ Qxd8 34.Qxe6+ Kg7 35.Be5+ Kh6 36.Bf4+ Kg7 1/2-1/2
I don't think any coach would say that you should only play opponents rated 600+ higher than you. Here's for example what Dan Heisman says, which I think makes a lot of sense:
Play mostly opponents 100-200 points higher than you - you need to be punished for your mistakes so you won't make them again...
...but don't completely stop playing opponents 100-200 points lower than you - they are the ones whom you have to learn to beat consistently.
In my opinion, it is also easier to stay motivated if you win at least some of the time. Playing much higher rated opponents from time to time is interesting, but I wouldn't do it exclusively.
Ultimately you have to do the analysis of "why did he do that" in game and under time pressure. Having it explained to you immediately post game is counterproductive. You need the opportunity to go away and analyze the game and then if you still do not understand it come back and talk to your opponent or coach about it. That way you learn to do the analysis yourself.
Consistently playing much stronger players gives you access to much richer learning experiences in this respect. If you remove the artificial objective of rating and aim to become a better player.
You learn from defeats when your mistakes are punished and made plain for you to see. You learn nothing from victories where your mistakes go unpunished and your ego is given an unwarranted boost.
No coach, by the way, advises that you play against opposition which is 600 points higher rated. That said you can still learn a lot from games against them. Try, for instance, to play lines which give you problems when you face them to see how the stronger player handles them. Then you can take that new knowledge back into your games against lower rated opposition.
Although I've never had serious coaching, most advice I have had revolves around making mistakes and attempting to learn from them. (Alongside structured opening and endgame theory etc)
This is best done by playing, and inevitably by playing opponents graded higher than yourself - although 600 points higher is unnecessary and you are unlikely to learn much from players that much higher rated.
For example, if you regularly lose to a player rated higher than yourself - you may find a pattern of ways in which you are losing, for example, creating weak pawn structures for yourself, or slow development. Not only working out what is missing from your game, you may also see aspects of opponents games which you then bring into your own playing style.
I've played for about 12 years now and the year in which I improved the most was when I was playing in a higher division against players averaging around 200-300 points higher than myself.
Also regarding opponents not giving post mortems, although useful, going through the game yourself to attempt to work out where you may have gone wrong or could improve can be just as useful than a player explaining how they beat you.
I believe it all comes down to the learning process. Having the possibility to play against players that are stronger than you is a strong asset that you should use most of the time.
Let me give you an example. You have 1400ELO. If you play against 2k+ you'll get destroyed every game. After that when you play against 1.6k and you are close to their level and learn the small differences of why you get beat. The other thing you do learn is how much of a difference there is between 1.6k and 2k+. It shows you how much you could learn and at what pace.
The important thing in this is seeing the differences and what you have to learn, just like at school/university at the first class you see the whole curriculum for the year. It sets your mind at peace and harmony and prepares it for the task at hand.
Hope this helps.
I am not sure how one coach's opinion makes it that all chess coaches are like that.
The best advice that I would give you as a coach would be "Play as many Open tournaments as possible" because in the Open category, you are likely to meet equal, weaker, stronger players and at the end of the tournament, you would have a lot of points to improve upon. Play with me on Chess dot com and I will be happy to give you a post-mortem of the game at the end of it.
To expose poor play and mistakes. To punish. To push the player to play better moves and learn new ideas.
All the obvious stuff.
Once you divorce yourself from your love of your rating, it's pretty obvious.
Edit: FYI - 200 point difference is sufficient. You should not play players consistently rated 600+ points above you. 200 is a good threshold. The same goes for reverse - don't play players frequently rated 200+ points below you. If you have the choice, always "play up".