We're using Smart Stats to analyse various aspects of cricket. In this article, we look at two wristspinners who have had a phenomenal run in T20s over the last year.

Since the start of the IPL last year, the two bowlers to have played the most matches and bowled the most deliveries in all T20s are Rashid Khan and Imran Tahir. The two are at opposite ends of their careers: Khan is 21, remarkable considering all that he has already achieved in T20 cricket, while 41-year-old Tahir is at the fag end of his career, but still a globetrotting T20 specialist. Both have been outstanding in T20, and by virtue of being wristspinners, demand for them across leagues is very high. While the common perception may be that Khan is the better bowler between them, the numbers provide a slightly different picture.

What do the traditional numbers tell us?
Wristspinners have been dominating T20 for a while now, and their main strength is picking up wickets at regular intervals without worrying too much about runs conceded. Khan has been so dominant over the last few years that it's possible some batsmen play the bowler rather than the ball against him. Over the last year, many teams have looked to play him out rather than trying to attack. As a result, he has picked up a wicket only once every 21 balls and has an economy rate of 6.9.

Tahir, on the other hand, might have slipped under the radar, but his numbers show he has been very effective. He has struck once every 14 balls and has conceded 6.7 runs per over. In the same period, the average economy rate for all wristspinners has been 7.5 runs per over, and the average strike rate 19.

How and where do they get their wickets?
Let us now dig a little deeper. Who bowls the tougher overs? Since IPL 2019, Khan and Tahir have bowled 14% and 18% of their overs respectively in the powerplay. Tahir has been impressive in this period of games, taking 12 wickets at an economy rate of 7.46, while Khan has only four wickets and has conceded 8.15 runs per over. Both have bowled the majority of their overs in the middle phase, conceding 6.24 and 6.34 respectively, though Tahir has the better strike rate - 13.6 to Khan's 20.6.

Although Tahir bowls only 13% of his overs at the death to Rashid's 20%, his showing has been pretty good in that phase too. One reason Tahir is more successful than Khan could be that batsmen have now found a method to tackle Khan by not attacking too much and thereby not losing their wickets. He might also be over-dependent on his googly: 37% of his wickets have come off that delivery, while the corresponding figure for Tahir is just 20%. That suggests Khan may need to add more variations in the coming year to get more wickets.

How do they fare on Smart Stats?
Tahir also has taken the more important wickets, as seen through the lens of Smart Wickets: 1.57 per game to Khan's 1.17. The Smart Wickets metric takes into account the quality of batsman dismissed, the score at which a batsman was dismissed, and the match situation at the time of the dismissal. Tahir has dismissed the likes of Tom Banton in the Blast, Babar Azam (twice), Andre Russell, Rishabh Pant, Colin Ingram and Alex Hales at crucial junctures in various games over the last year. He has broken key partnerships or dismissed the most important opposition batsmen early.

If we look at the impact created by the two bowlers in the teams they have played, Tahir again has a higher impact score: 50.6 per match, to Khan's 43.6. This impact score for bowlers considers the phase of the match in which they bowled, their economy rate (taking into account current and required run rates), the quality of batsmen dismissed, and the match context when the wickets were taken.

Tahir has been instrumental in winning matches for the teams he has played in, and created more impact with the ball than Khan. Dismissing Andre Russell at a crucial stage , Pant over at Chepauk, and taking the wickets of the run machine duo, Tom Banton and Babar Azam for Somerset are some examples of the impact created by Tahir.

On the Smart Economy Rate (SER) metric too, Tahir fares better. His SER is 5.97 while Khan's is 6.04. SER takes into account not just the overs bowled and runs conceded but also the match situation, in terms of how much pressure there was on the bowler at the time; the overall match run rate; how other bowlers fared; and the quality of batsmen the bowler bowled to.

Over the last year, Tahir has been the better and more impactful bowler of the two. Although he might be at the end of his career, his skills in the T20 format are still worth plenty. There might be a lot more focus and attention on Khan, but Tahir has consistently been putting up performances that have perhaps not been noticed as much.

Smart Stats is a part of Superstats, a new set of metrics used by ESPNcricinfo to tell more enriching and insightful numbers-based stories. More here.