If you are in a great bowling attack, the batsman is under constant pressure and your chances to average higher is well, much higher than if you are in a poor bowling attack, as the batsmen you face (unless you are the opening bowler) are all set and they can just play you out.
Ofcourse, you have more competition for wickets in a good bowling attack and as a result, its harder to average 5-6 wickets/match.
Result ? If you are about equal in capability to me and you bowl in a poor attack, your average should be worse but you should have more wickets/match ratio than me....
Yeah but you're not disagreeing with me by saying this.
Murali's match/wicket ratio is affected in exactly the way you just described, yet what's the most oft-quoted statistic to 'prove' Murali's dominance over everyone? Match/wicket ratio. It certainly does follow logically that a great bowler amongst lesser peers will get many more wickets per match than another in a great attack for the reasons you described. So why then do people say that stat proves Murali a superior bowler when there are logical reasons for why his match/wicket ratio is higher (i.e. getting more of the ball and less great bowlers competing for wickets)? You have to admit; Murali DOES bowl an awful lot more overs than the other bowlers and bowls a lot of balls for his wickets. Of course, his average isn't affected by this but strike-rate is and Murali's is 57.51 vs 58.44 for Warne. That's not much of a difference, particularly since it can be said that Murali has played significantly more on 'helpful' pitches. That said, I don't think this is as huge an advantage as people will tell you because Warnie's bowling is geared towards harder/bouncier pitches and it wouldn't be easy to adapt (and vice versa).
Which is why when you take away McGrath and leave Warney with just Gillespie-Fleming-Kaspa-Lee-Reiffel etc ( a decent attack), his average shoots up but his wicket-taking also improves.
Which is why i think if you exchange Murali for Warney in the Aussey team, Murali probably wont average 5 wickets per match but will average better.....but since his average and wicket/match are both better than Warney's, i consider him to be a superior bowler.
See I think the difference in average only partly reflects ability. Leg-spin, for mine, will always be a tougher art to excel in not just because of the greater physical demands (doesn't really apply here as Murali's action is so unorthodox that he probably puts as much physical effort in as Warnie) but because of the line one has to bowl to do off-spin vs leg-spin. No matter how much the ball is turning, for a right-hander of quality, a bowler who has to aim for a leg-stump line will always be easier to score off than an off-side line, even when the ball is turning. There is always going to be a greater probability of what any batsman would consider to be a 'loose' delivery on a bowler who bowls leg-stump than off-stump. Indian players show this more than most; the reason they dominate Warne and every leggie who's been to India probably since India started playing Tests is because they are excellent at waiting on the ball and seeing the spin before playing it off the back-foot but to the full-balls, are outstanding at leg-side shots like flicks, glances, lofted-drives, etc.
Plus, there are far less fielders on the leg-side in just about any given Test-match situation (a 5-4 off-side field is about as leg-side as any international captain gets in Tests and even then, it's way more rare than a 6-3) so logically, a leg-spinner is always more likely to go for more runs, hence higher average. Because the number balls that constitute a 'match' can vary so widely (from 3 days to 5 days), I don't think wickets/match is as relevant a stat as something like strike-rate and as pointed out above, they are very similar.
So in my view, the differences in their averages is more reflective of the lower-percentage nature of a leg-stump line than raw ability. Forgetting the raw data, having seen plenty of them both (a little more of Warne, obviously), I can't separate them. They both spin the ball miles, both have excellent variation both exaggerated (leggie vs wrong'un, offie vs doosra) and subtle (both have about 5 different balls which go straight on, varying only in flight, bounce or pace), excellent sliders and both, on their days, run through opposition batting line-ups with ease. If someone asked me to pick, I just can't. Sorry.