Just how good is Dale Steyn? Outstanding, right? Almost everyone will agree he is an all-time great. But as he stands on the verge of breaking the record for South Africa's most Test wickets, requiring one more dismissal to go clear of Shaun Pollock, the numbers suggest he has been even better than he is in most people's estimation. It may be that Steyn is not merely great, but is actually among the finest half-dozen quicks to ever have played the game.

We will eventually measure Steyn's record in relation to the best quicks through cricket's modern history, but before that let's look at how he compares to his 21st-century peers. Among fast bowlers who have taken over 200 wickets since 2000, Steyn's average of 22.42 is third-best, behind those of Glenn McGrath and Vernon Philander. While McGrath was experiencing a late-career harvest (his overall numbers are slightly worse), Philander is buoyed by spectacular numbers while playing at home - he has been nowhere near as effective as Steyn outside South Africa, and his returns in Asia have been particularly modest relative to his exploits elsewhere.

Where Steyn is a clear leader, however, is in strike rate; no one else on the list gets close to his 41.6. He is also the second-highest wicket-taker for this period, with 421 scalps. Only James Anderson has been more successful, but Anderson's average (27.23) and strike rate (56.2), are not in Steyn's league. This is no real surprise - although Anderson has been a supremely skillful bowler, Steyn could do pretty much everything Anderson could do, but at 10kph faster.

How Steyn stacks up against other fast bowlers of his era Ishita Mazumder / © ESPNcricinfo Ltd

Among Steyn's clearest claims to greatness have been his performances in Asia, where quicks generally encounter the least helpful surfaces. He has 92 wickets in the continent, well clear of Anderson, who is the next-most-successful non-Asian seamer this century with 59 wickets. Among quicks to have played at least 20 Tests in Asia since 2000, though, Steyn's numbers compare favourably even with those of Asian fast bowlers. His numbers are virtually indistinguishable from those of Shoaib Akhtar, with other wonderful Asian quicks - the likes of Chaminda Vaas and Zaheer Khan - sitting way back.

The best Test fast bowlers in Asia since 2000 Ishita Mazumder / © ESPNcricinfo Ltd

We have now established that Steyn is the most penetrative and versatile quick of the last 15 years, but let's now look a little further back and bring the great '90s bowlers into the frame. To do a meaningful comparison across eras, though, we must account for varying conditions and trends. Although bowler-friendly tracks have made a roaring comeback over the past few years, much of Steyn's career was played in an infamously batting-friendly period. So instead of merely stacking up these players' averages and strike rates against each other, let's look at how much better each bowler was than his peers, by calculating the difference between each bowler's numbers and the mean bowling numbers in his career span (that is, the mean bowling stats from between the bowler's first and last Test).

From among a group of eight truly outstanding quicks, Steyn has the best average differential, though he is neck-and-neck with McGrath.

Quicks compared to others in their career span Bowler Wickets Average Other quicks' Ave Average differential Dale Steyn 421 22.42 32.81 -10.38 Glenn McGrath 563 21.64 32.00 -10.36 Shaun Pollock 421 23.11 32.36 -9.25 Curtly Ambrose 405 20.99 30.00 -9.01 Allan Donald 330 22.25 30.50 -8.25 Waqar Younis 373 23.56 30.55 -6.99 Wasim Akram 414 23.62 30.37 -6.75 Courtney Walsh 519 24.44 30.04 -5.60

Where Steyn sets himself apart from McGrath, however, is via that incredible strike rate. Only Waqar Younis had a better strike rate differential than Steyn, but then Waqar was more expensive as well.

How much better is Steyn over others in his era? Ishita Mazumder / © ESPNcricinfo Ltd

Where Steyn's versatility - owing probably to his mastery of reverse-swing - really become clear is when his figures in Asia are compared to those of the best visiting quicks through cricket's history. His raw average and strike rate in Asia is staggering enough, but throw the differential numbers in - that is, compare Steyn's stats to the mean for his era, while doing the same for the other non-Asian greats - he comes out ahead of the pack in terms of average.

How Steyn's numbers in Asia stack up against the rest ESPNcricinfo Ltd

On strike rate, Steyn and Wes Hall are well clear of the rest. Effectively, Steyn's wickets in Asia have come an astounding 28 balls closer together than they have for the average bowler in his era.

ESPNcricinfo's jury panel recently voted in McGrath as the right-arm quick in our Test team of the last 25 years, but given the above numbers, I would replace McGrath with Steyn, owing not only to Steyn's prowess on the toughest continent for quicks, but also because of the value he adds via his strike rate. A full fifth of McGrath's wickets had also come against minnows, by which of course I mean England 1994 through 2003.

Even Malcolm Marshall, whose record in Asia is what clinches him the "greatest fast bowler ever" tag, for many, was not quite as statistically dominant as Steyn has been there.

Is Steyn the greatest-ever non-Asian quick bowler in Asia? Ishita Mazumder / © ESPNcricinfo Ltd

By now, it is clear that numbers-wise, Steyn has a strong claim to being the finest fast bowler of the last 30 years - in a fairly crowded field. He is also almost certainly the best non-Asian quick in Asian conditions. Among bowlers of any ilk with more than 200 wickets, from any era, Steyn's career strike rate of 41.6 is the best. If you are a captain in need of quick wickets, with minimal release of pressure, there is no better player to call on from your great-bowler rolodex than Steyn; he is the most aggressive great bowler there has been.

Strike rates for bowlers with over 200 wickets Bowler Innings Wickets Average Strike rate Dale Steyn 159 421 22.42 41.60 Waqar Younis 154 373 23.56 43.40 Malcolm Marshall 151 376 20.94 46.70 Alan Donald 129 330 22.25 47.00 Vernon Philander 103 205 21.54 48.60 Fred Trueman 127 307 21.57 49.40 Jeol Garner 111 259 20.97 50.80 Richard Hadlee 150 431 22.29 50.80

Finally, one more figure that puts Steyn in the league of the most sublime quicks to ever bear down on batsmen: his record in victories. Aside from the first few years of his career, in which Australia dominated, South Africa have arguably been the best Test team in the world for a good portion of Steyn's career. In that time, no bowler has been more crucial to his team's success. In fact, few quicks have ever been as impactful for any team as Steyn. Of bowlers that played in the last 100 years, only Richard Hadlee and Imran Khan have better averages in victories (minimum: 100 wickets in wins). Steyn has more wickets in wins than the other top 15 bowlers (by average). It pretty much goes without saying by this stage that Steyn's rocking strike rate is the best. Fast bowlers in team victories (qual: 100 wickets) Bowler Innings Wickets Average Strike rate Richard Hadlee 44 173 13.06 33.50 Imran Khan 46 155 14.50 38.29 Dale Steyn 88 293 16.10 31.50 Malcolm Marshall 86 254 16.78 38.10 Alan Donald 64 187 16.79 35.50 Curtly Ambrose 87 229 16.86 44.40 Vernon Philander 64 145 17.17 40.40 Fred Trueman 68 177 17.30 40.79

With all these numbers considered and put into historical context, Steyn's career comes out looking even more monstrous than perhaps he has got credit for. How many bowlers in history can claim to have dominated matches in Galle (in 2014), as well as at the Wanderers? There is stiff competition for the pace-bowling spots in an all-time XI, but having been the clear leader during his playing period, and having put up spectacular numbers despite playing in one of the most batting-friendly eras in history, he deserves to be part of any all-time XI conversation.

With stats inputs from S Rajesh