In an AFL draft class that has been tipped as the best in 15 years, there seems like no way to lose if you have pick number one.

But what do you do if you're Carlton tonight?

Do the Blues go with the safe choice of an elite runner in Victorian midfielder Sam Walsh, or do they opt for a "make or break" pick like South Australian star forward Jack Lukosius, who has been described as a potential "generational" player with the ability to see ahead of the play?

Do the benefits of grabbing a game-changer for the side that finished bottom of the ladder last season outweigh the cautionary tales of some top selections that have gone wrong for teams in recent years?

Prospective first draft pick Sam Walsh would be a 'safe' option for many clubs. ( AAP: David Crosling )

In the past decade, half of the number one picks have been key position players: Jack Watts (2008), Jonathon Patton (2010), Tom Boyd (2013), Paddy McCartin (2014), and Jacob Weitering (2015).

Arguably, none are yet to fulfil the lofty expectations that come with being the league's first overall draft choice.

The height and the talent curve

Those players filling key positions are necessarily tall, even by AFL standards (more than third of whom are already above the average for young Australian men).

As such the pool of talent to choose from is thus already reduced. And this presents a dilemma for clubs at the draft.

Should they reach for a taller player at a higher position than their talent would otherwise dictate, or should they settle for the sure-fire small midfielder?

We have analysed every draftee between 1993 and 2007 (excluding father-son, academy and scholarship selections), and rated their career performance. We have done this by using a metric called Player Approximate Value (PAV), which quantifies an individual's attacking, defensive and midfield contributions to their team.

In general, the deeper the talent pool at a certain height, the easier it is pick successfully.

In a position to pick

Taking this a step further, we have used PAV to sort everyone in our sample who has played at least one AFL match into six different "types". The categories are based on the players' height and the part of the ground they most contributed to during their career.

The six player types identified are: Key Position Defenders (KPDs); Key Position Forwards (KPFs); Midfielders; Rucks; General Defenders; and General Forwards

While they may over-simplify the roles of footballers in the modern era, the categories are helpful in identifying broad trends in player performance.

Midfielders are the most "sure thing" at the top of the draft

Our first major finding is that midfielders selected in the top ten have performed better than other players taken in that range.

From 1993 to 2007, 42 of the 134 top-10 selections (31 per cent) were midfielders. Almost 70 per cent of the midfielders picked inside the top 10 produced more than 100 PAV, meaning their careers were among the top quarter of all players. Just over 57 per cent of top 10 selected midfielders produced more than the average produced by players selected at pick one (147 career PAV).

This bodes well for the prospects of Walsh, but what about Lukosius?

As you can see in the above graph, the hit rate for grabbing a long term key position forward at the top of the draft is significantly worse than for midfielders.

Of the 24 KPFs grabbed inside the top ten in our sample, less than half (46 per cent) went onto produce more than 100 PAV, and just three in eight (38 per cent) produced the equivalent of the average pick one.

We tend to remember the success stories, while forgetting the failures. For every Lance Franklin and Jarryd Roughead, there is a Mitch Thorp and Beau Dowler. All four were key position forwards drafted by Hawthorn inside the top ten between 2004 and 2006.

Other positional groups are also generally more fraught than midfielders, with the exception of the few rucks taken at the pointy end of the draft.

2018 All-Australian key forward Jack Riewoldt was a top 20 pick when he was drafted. ( AAP: Hamish Blair )

Across the rest of the draft, the rates of success for all types of players drops away nearly uniformly. Smaller players (midfielders, general forwards and defenders) hold their value through the rest of the top 20, while the performance of key defenders actually improves slightly.

The rate of success of key forwards drops by half outside the top ten, and by half again into the 20s, before actually rebounding a little later in the draft. The success rates for all types of player become pretty uniform from about pick 40 onward.

And in recent years?

To see if this trend holds in recent years (2008-2014), of which the draft cohorts are mostly still active, we can shift to comparing players to their draft peer group. We have scored each draftee in percentage terms, relative to the best draftee from that year to date, wherever they were selected.

The closer an aggregate score is to 100 per cent, the better a draft group has performed as a whole. We have also shown the 1993-2007 group in these terms as a comparison.

Success rates for smaller players have spread to include forwards and defenders, while the success of key position forwards selected outside the top 10 has also risen slightly.

In short, the rates of success for midfielders and key forwards appear to be broadly consistent with the 1993-2007 drafts.

So where are all the other key position forwards?

For the analysis above, we have excluded father-son, academy and priority access selections, but those mechanisms seem to have had a disproportionate impact on the availability of key forwards.

Due to compromises in the draft pool, some of the names unavailable to the general talent pool have included: Jeremy Cameron, Joe Daniher, Tom Hawkins, Travis Cloke, Jonathan Brown, Taylor Walker, Matthew Richardson, Jarrad Waite, Charlie Dixon, Lance Whitnall and Darcy Moore.

With the small number of key position forwards in each draft pool, these carve-outs seem to have had a major impact on the likelihood of picking a successful KPF prospect early.

South Australian star forward Jack Lukosius has been described as a potential "generational" player. ( AAP: Andy Brownbill )

Of the four key forwards in the 2018 All-Australian Squad, one was chosen in the top ten (Franklin), one inside the top 20 (Jack Riewoldt), while Ben Brown came at pick 47 and Hawkins joined the Cats as a father-son selection.

That player source mix is relatively consistent over the past decade. Players selected outside the general draft process are regularly among the most successful key forwards each year.

Key forwards are hard to find, so positional need can push players up the draft board. Priority access has increased key forward scarcity, intensifying the need to find them elsewhere. Clubs regularly pay a premium for big forwards.

They can do it via trading or free agency, but the opportunity to sign a Franklin or Jesse Hogan or Tom Lynch is also pretty scarce.

Often, the only option is risking a high draft pick. And that is at the heart of the dilemma faced by recruiters making plans going in to the draft period.

Good luck, Blues, history suggests you might need it.