Here are some sequences of six numbers. What connects them?

8, 13, 16, 2, 68, 11

13, 2, 16, 15, 1, 7

43, 31, 38, 12, 0, 43

17, 7, 26, 13, 6, 37

0, 4, 59, 0, 0, 9

No, they're not Tiger Woods' latest scorecards. They're the last six innings of Joe Root, Nick Compton, Michael Carberry, Sam Robson and Jonathan Trott before they were replaced (or in the case of Trott, retired) as England's opening batsmen.

And here's another: Adam Lyth's last five read 24, 6, 37, 0, 7, a sequence that in the light of those above, has an ominous familiarity. What may break Lyth out of this pattern and give him the chance to extend his run beyond another innings or two is expedience: England are burning through openers so quickly, there aren't too many left in the queue.

It's easy enough to pick through the conventional wisdom for the reasons behind these sudden departures. Excluding Root, returned to the bosom of the middle order, and Trott, Compton was overly technical and obsessive, Carberry couldn't turn starts into big runs, Robson could be beaten on both sides of the bat, and Lyth will go at wide deliveries on the back foot.

"It is the hardest place to begin a career in Test cricket because the examination is total and the scrutiny minute - the yawning eye of television and the overwhelming immediacy of social media converge in the rush to judgement"

But to do so focuses narrowly on individual troubles. Is there a wider causality? And what is happening to these players once they are dropped? Why are they no longer scoring the runs that they were and demanding re-selection?

Opening the batting in Test cricket is hard. It's hard on the body, hard on the mind, hard on the soul. None of Test cricket's top ten run scorers are openers (some may have opened occasionally - not the same thing). It is batting at the sharp end, and it acts like a can-opener on a candidate's game and his psyche. It is the hardest place to begin a career in Test cricket because the examination is total and the scrutiny minute - the yawning eye of television and the overwhelming immediacy of social media converge in the rush to judgement.

The brand new Test match opener must contend with his partner, in England's case Alastair Cook, who will also be his captain. How easy is it to establish a working relationship with a player who will also have a call over your future? He has played 100 Test matches. It's his office you're sharing.

Failure for an opener is harder to bury. It has an immediate impact on the match. It ratchets up pressure on everyone from the coach to the middle order. It is a weight for others to bear. A No. 5 with, for example, Carberry's run of scores - 43, 31, 38, 12, 0, 43 - would be "due". No one would be chucking them out of the team.

Graham Gooch has a word with Nick Compton Getty Images

It's interesting that Compton, Robson and Lyth all made hundreds early in their careers but still found themselves under threat. The results of an opener are just perceived differently.

Then there is the raw and bloody nature of the batting itself. "You don't face that kind of pace in county cricket," Cook said after Mitchell Johnson had melted faces at Lord's. "You may get one quick bowler. You won't get three." The standard of county wickets means that the putative Test opener is more likely to be nicking off to Darren Stevens or Jesse Ryder than at the business end of raw pace.

It was not always so. Alan Butcher wrote a lovely piece for ESPNcricinfo, "What Sylvester Clarke taught me", about the experience of facing the battery of quick bowlers that stalked the county summers of the 1970s and '80s: Imran Khan, Wayne Daniel, Malcolm Marshall et al. Butcher was a superb player of fast bowling who was limited to a single Test, in part because along with Geoff Boycott and Graham Gooch, there were several others forged in this unforgiving school that could do the job. The jump up then was nowhere near as high.

International cricket is a thing apart now, a hermetically sealed world of travel and pressure that cannot be replicated at a lower level. Other countries seem to take this leap of faith more easily than England. A new-world attacking opener like Alex Hales may well have played for Australia or India before his contemporaries. It would be interesting to see the reaction to him in an England shirt alongside Cook. Would his inevitable failures be given more or less time, given that his successes are likely to be spectacular and game shaping?

Players are due a duty of care too. It has not been pleasant to see how much rejection has hurt Compton, who has been open about his feelings, and Carberry. Robson is taking a season to recover. George Dobell revealed the details of a row between Compton and the England team management over a rib injury that had kept him from the field. Like Pietersen, it appears his face didn't fit.

The lack of an established partner for Cook is adding to his list of troubles, and he has more than enough of those to concern him. If Trevor Bayliss is as astute as he seems, he will be driving at the cause of the problem rather than just pulling the next cab off the rank.