There are no guarantees in sport, but around this time of the year, tennis comes close to offering one. Rafael Nadal's unrelenting pursuit of clay-court titles means by the time the Roland Garros final rolls around, you can be fairly confident it'll be a left-handed sleeveless Spaniard with his hands (and teeth) around the Coupe des Mousquetaires trophy.
But with the Pakistan Super League, which Covid-19 has forced to take place alongside Roland Garros, Pakistan's premier T20 competition supplies a certainty of its own. When Lahore Qalandars take on Islamabad United in the first game of the PSL's second leg, you will find the captain who calls correctly at the toss opting to put the opponent in to bat. This trend will continue - probably for every one of the 20 remaining games - with the chasing side likely to win a majority of those.
That would be true regardless of the teams playing that first match, but Islamabad United's involvement makes that guarantee even easier to provide. The two-time champions have never entertained the notion of batting first in six seasons of the PSL, and the data - which United are known to swear by - vindicates them. In 28 matches that United have chased targets, they have successfully achieved 23 of them, a win percentage over 82%. By contrast, on the 29 occasions they were asked to bat first, they have lost 21 matches.
United's lop-sided numbers might look like an outlier, but the franchise isn't the extreme case, it's the league itself that is. Exactly two-thirds of PSL games since the 2017 season have ended up in a win for the chasing side, far and away the highest proportion among elite franchise T20 leagues. The Africa T20 Cup's 55.8% is the second-highest percentage in that time, with the IPL third; 53.6% of games are won by the side chasing. The Big Bash League and the Vitality Blast are the only premier T20 franchise tournaments where batting first has carried a historical advantage, with chasing sides winning 48.7% and 45.4% of times respectively.
While it was fairly obvious the PSL was unique in terms of the extent of the advantage chasing sides seem to carry, the trend was turbocharged this year. With all group games in the first phase of the PSL in March taking place at the National Stadium in Karachi, every single one of the first 13 games was won by the side that won the toss and bowled first (which all of them did). The 14th game, and as it happened, the last one before the Covid-enforced postponement, was the only time a total was defended, with Quetta Gladiators beating Multan Sultans by 22 runs.
It's hard to pinpoint precisely what makes the PSL such a chasing dominant league, but Islamabad United head coach Johan Botha feels there was a psychological element to it this year. "I think initially in Karachi with teams chasing so well, conditions played quite a bit of a part in that," he told ESPNcricinfo. "After four, five, six games, teams seemed to not be able to defend and it became a little bit of a psychological thing. So I think that's where it got to teams. And then a few teams just somehow managed to do some silly things while defending - drop a catch of a key player, a big over at the wrong time to create momentum for the chasing team, and so on. All of those things just seem to play out beautifully for the chasing teams.
"We were another team that chased pretty well in the initial leg. We had some firepower at the top with Alex Hales, Paul Stirling, Shadab Khan as well as a few of our young guys. I still think defending is not impossible, but you just have to take those little opportunities, build enough pressure for the opposition to make mistakes. I remember we had the one loss when we batted first, and I think that was maybe just a hangover from the game before because it was a double-header day and we saw the team before us. It was a high-scoring game and we thought we needed 180 and we batted really poorly to get maybe close to 130. That was a lesson for us as a team that you've got to play what's ahead of you and you can't play what happened to forty overs before our game. That was a good learning curve."
There are more unknowns at the PSL than perhaps any other league, and Botha pointed out when teams are unsure, they retreat into the comfort zone of wanting to know the target. Since the league began, there have been several venue changes, most commonly because of the PCB's ever-increasing desire to bring more matches to Pakistan, and the precariousness of the security situation in the country. In 2017, the final was held at the Gaddafi Stadium in Lahore, while four matches were played in Pakistan in 2018. Last year, the PSL went to places like Multan, where sides would have very limited ideas of conditions and little experience to draw on.
With games starting at three different times in Abu Dhabi over the next two weeks, the role dew might play throws in another unknown into the mix. On the eve of the tournament, Karachi Kings captain Imad Wasim said he had "never seen as much dew in Abu Dhabi as I did a couple of nights", but also that there was little during the day.
"It was quite alarming, the dew," he said. "It's complicated and we'll just have to wait and see how it plays out during tournaments. The matches start late enough that the dew factor is equal for sides batting or chasing first, and so the toss doesn't matter quite as much." Even so, it offers even more incentive for the side calling correctly at the toss to send in the opposition first.
In 2016, 21% of sides that won the toss batted first, but that dropped to four percent (just one game) the following year. In the last three seasons, just six sides have opted to bat first in 80 matches. PSL 2018 was the exception, with a third of the sides looking to set a target. Sure enough, that's the only year fielding first after winning the toss wasn't a successful strategy; the side choosing to do that won just 11 of 23 games. That was despite 2018 being a year inveterate chasers United went on to win the whole thing including six of the seven games they chased. In the final, Peshawar Zalmi, the only side to defend a total against them that year, notably won the toss and decided to let Islamabad field first again; it ended up costing them the title.
The PSL also seems to offer a unique advantage to chasers in the early stages of tournaments. In the first 15 games of each season, chasing sides are staggering successful, even by the PSL's already inflated standards. Forty three of 58 such games see the chasing side triumph, a win percentage of nearly 75%. In the CPL, IPL and the BBL, win percentages for chasing sides in the first 15 games actually drop below the overall average; the same numbers read 52%, 44.7%, and 46% respectively.
"Maybe that's the safe option: win the toss, bowl first and then you know what you chase," Botha says. "I think that's a big trend around the world. Just so you don't overshoot with the bat in the first innings or look for too much. Because then you get blown out the water and you either need to get early wickets in the second innings or they have to bat poorly for you to have a chance in the game. So I do think the trend might continue."
If precedent is any guide, there's little reason to argue with Botha's conclusions. With Nadal in the quarter-finals of Roland Garros having won 13 of the last 16 titles in Paris, precedent does seem to be a guide after all.

Danyal Rasool is a sub-editor at ESPNcricinfo. @Danny61000