Originally Posted by JRC67
... On most wickets the traditional balanced attack isn't that relevant since the demise of uncovered wickets and teams have a pretty good idea of how a pitch will play out. The advent of reverse swing has also played against this as on dry pitches a seamer who can reverse it remains a threat during the traditional spin time of 40 - 80 overs. ...
These are two factors often mentioned in defence of opting for the extra seamer, but I think both are easily overstated.
On the first point, I think pundits and selectors are still often surprised by the way test match pitches play. When there is an unexpected amount of assistance for the seam bowlers, the bowling attack that has been selected tends to be perfectly adequate to the task; sometimes in such cases the spinner and/or the fourth seamer won't get a bowl. More notable as far as selection of the bowling attack is concerned are the instances when the pitch offers unexpectedly little assistance for the seamers. It may be that he is slightly old-fashioned, but Geoff Boycott is fairly often heard to say that because of the way a pitch has turned out, he's sorry England didn't pick an extra spinner. And he's not alone; and it's not always the case that the second spinner, who hasn't been picked, is from Yorkshire.
I think that test teams have got used to shrugging off their sometimes unfortunate lack of a second spinner because usually in order to fit in the second spinner they would have had to drop either their third seamer or a batsman, and so they don't think it's worth it unless they can tell in advance that the pitch will be a raging bunsen. But England are now in a special position in that regard, because if they were to call Stokes their third seamer and pick a reliable spinner, then they could pick a second spinner (e.g. Rashid, Patel, Ali, Ansari) who is so good at batting that it wouldn't matter much if he hardly bowled in some matches.
As for reverse swing, I think it's still quite rare to find a bowler who can do it reliably. Bresnan was associated with that art for a while, and it may be partly due to that that he was picked instead of Panesar in this famous match
. Also, it's something that you wouldn't necessarily have to pick an extra player for, because you're always going to have two or more seamers in the team, and if it's reversing they should be able to reverse it; whereas if it's turning nicely you would want to be able to put a spinner on at both ends. More generally, I don't think reverse swing should be thought to be a functional alternative to spin bowling, because the former is dependent on the age and state of the ball and so may come and go relatively swiftly, whereas the latter is more dependent on the state and age of the pitch, and so can come into play quite consistently towards the end of the game.