THE NAB AFL Under-18 Championships offer recruiters the best opportunity to watch, study and compare the best draft hopefuls in the country. 

Some of the teenagers are trying to prove themselves, while others have already proved enough to get drafted, with clubs now having to work out where they sit in order. 

Ahead of the championships, which begin this weekend, AFL.com.au has ranked the top 20 prospects (in alphabetical order) to watch throughout the carnival.  

Mobile midfielder who can push back, forward or anywhere on the ground. Acres is a strong runner, and makes the right decisions, but may have only limited exposure in the championships after sustaining a shoulder injury this month. He will keep training and testing the injury in the hope he can avoid surgery. 

Aish enters the championships after a long layoff after a shoulder reconstruction last year. Has a strong bloodline of football, and Aish has already added a new chapter with a senior premiership in the SANFL last year. Nicely sized wingman who is a natural footballer: he gets the ball and finds his teammates, makes the right decisions, and always seems to think ahead of others. 

Grew in prominence with a brilliant campaign last year, starring for Vic Metro and the Oakleigh Chargers at TAC Cup level. Billings is a smart and skilful half-forward with elite foot skills and a strong overhead mark. The composed and driven 17-year-old is likely to see some more midfield action this year.  

The athletic utility has a few unique skills. Bontempelli is tall enough to hold down a key position, and runs and jumps at marking contests like one, but can also push up the field and is good at ground level. Has been starring for school side Marcellin College.  

Big, strong marking and straight kicking forward who is the standout tall of the draft. Played for Vic Metro last year and kicked four goals against Vic Country, but has improved since then and is an even more dominant player. Opponents will find him very hard to stop. 

A broken finger sustained earlier this month will delay Crouch's start to the championships. But it shouldn't change his ranking as one of the better inside midfielders of the draft. Crouch digs into contests, rips the ball out and feeds it off, and has improved his outside play.  

A strong and physical midfielder who thrives on the contested situation. The South Australian has a presence around the ball and swings onto his left foot with ease. 

Solidly built midfielder who does everything well. Isn't afraid to put his head over the ball to win it, but has also shown he can use it when it's in his hands. Well-rounded player who attacks the ball and recently made his senior SANFL debut.   

A strong-bodied midfielder who fiercely attacks the ball and contest. Will help lead Vic Metro's on-ball department and has also shown a tendency to push forward and hit the scoreboard. 

Gardiner's competitiveness puts him in this bracket. As perhaps the best tall defender of the draft, Gardiner is quick to read the ball in the air and finds a way to effect a spoil. Most of all he hates being beaten - the perfect quality for a backman. 

Hartung has had an interrupted start to this year after finger surgery but there is little doubt of his talent. A midfielder who shifts forward, Hartung possesses brilliant foot skills on his left and right boot, and an extraordinary endurance base.  

Talented left-footed midfielder who was close to being mini-drafted last year. Kelly is composed with the ball and uses it well, and shone at last year's championships against players older and bigger than him. Can run all day, which complements his other traits. 

Named Oakleigh Chargers co-captain after an impressive season last year. Small forward with extreme pace and goal sense, but also an ability to work up the ground. One of the smaller prospects but has a lot of tricks. 

The late call-up to the AIS-AFL Academy has some style about him. Is generally used as a rebounding and attacking half-back flanker or a creative wingman, where his run and decision-making has caught eyes. Perfectly sized to play a range of roles in the modern game.  

An exciting half-forward who is great mark above his head and one of the best kicks of the draft. Had a taste of Vic Metro action last year and will be better for it this time. Started the year in strong form and might even see some time through the midfield. 

North Melbourne will use its first pick at the draft on McDonald, having already committed to him as a father-son selection. They're likely to get a bargain, too, with McDonald one of the top prospects. Has played mainly off a half-back flank, where his raking left-foot kick, footy instincts and competitiveness have been suited.

A smooth-moving and classy left-footed midfielder who also played a role for Vic Metro last year as it went on to win the division one title. Has a damaging kick and often sets up play as the linkman through the middle of the ground. 

Versatile, athletic and competitive, Scharenberg can play at both ends of the ground and might even end up a midfielder. Generally plays as either a second tall forward or defender and is valuable in both roles. Marks well and already has a mature body.  

Taylor is a player who makes things happen. Although small, the Geelong Falcon wins his own footy and runs with it, taking opponents on with his pace or a crafty sidestep. Has shown he can use his creativity in the midfield or closer to goal. 

Wasley-Black has played nearly everywhere in his junior career but now seems settled off a half-back flank. He has some attacking traits and is comfortable with the ball in hand. GWS has automatic access to recruit Wasley-Black under the AFL's list-building rules, if the Giants want him.