In sport, as in life, we often talk about the "sliding doors moment", as if such interventions create completely new timelines for the protagonists to inhabit. But outside of a movie script, the threads are often a lot more tangled. "What if Jonny Bairstow hadn't hurt his ankle playing football in Sri Lanka, allowing Ben Foakes to win Man of the Match on debut and keep the gloves for the rest of his career all of five Tests before Bairstow returned, only to be dropped at the end of the summer for Jos Buttler…?"

And here we are, back in Sri Lanka two-and-a-bit years on. Bairstow is champing at the bit for a Test recall, though this time as a batsman only. Foakes hasn't played since the tour of West Indies in early 2019, despite being regarded by some as the best wicketkeeper in the world. And Buttler is in possession of the gloves, fresh from a summer that seemed to encapsulate all of the main arguments for and against his position in the Test side.

Joe Root has already indicated that Buttler, who scored a career-best 152 in his last Test innings, is the default pick to keep in Galle next week - so maybe there's no debate to be had. But with the selectors set to give Buttler time off during the India tour that follows, and Foakes primed for another rare opportunity, it's worth having our arguments rehearsed.

Since retaking gloves in New Zealand last winter, Buttler has scored 574 runs at 33.76. That mirrors almost exactly his overall Test average of 33.90 - a number which breaks down to 35.68 when playing as a specialist batsman, and 32.35 as keeper. So far so underwhelming, perhaps, at least for a player as exceedingly talented as Buttler, arguably England's greatest one-day batsman of all. But what about the other side of the game? The skill which you don't want to be noticed for.

According to ESPNcricinfo's data, in 11 Tests Buttler has taken 37 catches and been responsible for five drops. But while his catching success has been up at 94.6% off pace bowling, he has just two catches to go with three drops off spin. Dom Bess, England's first-choice spinner over the last 12 months, will doubtless remember one of those misses: Shan Masood put down on 45 during his 156 at Old Trafford (Buttler also missed a stumping chance off Bess a few overs later).

However, that sliding doors moment came with Buttler in the foothills of his resurgence as a Test batsman - it was his escape-artist 75 from 101 balls in the fourth innings that won England the game. Similarly, although one of his pace-bowling drops was likely pivotal - Jermaine Blackwood put down early on the way to a match-sealing 95 at Southampton - England came back to claim the series against West Indies 2-1, with Buttler producing his first Test fifty for 14 innings.

Buttler, to his credit, knows all about the vagaries of form and fortune. He made a golden duck in England's intra-squad game on Friday, and will have precious little time to get match ready for the challenge of keeping wicket in Sri Lanka, where conditions demand every ounce of concentration behind the stumps. "As an allrounder you want everything firing," he said before England departed from Hambantota on Saturday. "I know it's going to be a great challenge for me with the bat and the gloves."

Amidst all the hours of preparation, the squatting and leaping and catching, he will have the memory of that second Test hundred in his back pocket, too. "It's the start of a new year so it doesn't count for much, except it gave me a lot of confidence and hopefully I can still ride off the back of that confidence, even though it's a long time ago. It's nice to be in the position where I finished the summer strongly."

Two years ago, after Foakes' debut in Galle, Buttler described it as "a wake-up call [about] the level you need to get to" (as well as scoring a hundred, Foakes took two catches, effected a stumping, and didn't concede a bye). In his short Test career, Foakes averages 41.50 and has only dropped one catch - an understudy in name only.

"He is a fantastic player and was Man of the Series last time in Sri Lanka," Buttler said. "Someone like Foakesy is a great person to push my game on. I've watched him practise and he's impressive to watch, fantastic to see how good he is. Competition for places is healthy and can drive people on and give people hunger to improve and perform. In all departments on this tour, there is a lot of competition."

Buttler can also look back fondly on England's 3-0 win in 2018-19, when his 250 runs as a specialist batsman came at an average of 41.66 and, more importantly, a strike rate of 72.04 - the highest on either side. Whether he can give England's middle order the same attacking intent while balancing the demands of sweat-soaked hours on his haunches will be an intriguing subplot of the tour - though hardly definitive, with Foakes expected to come in against India regardless. Not so much sliding as revolving doors.

"I really enjoyed the cricket here last time," Buttler said. "It was fun. It was quite different for us as an England team, dominated by our spin bowlers and playing spin, a lot of men round the bat. I found that really enjoyable, quite different to what we're used to. I enjoy playing spin and the challenges it presents, quite different to a lot of the cricket we play. I'm really looking forward to it

"Every time you turn up, you have to work out the conditions and how you are going to play against the bowlers you're up against. It is dangerous, I think, to go in with too many pre-conceived ideas."

Ahead of six Tests on the subcontinent, the same could be said for England's wicketkeeper debate.

Alan Gardner is a deputy editor at ESPNcricinfo. @alanroderick