AFL W2W4, R21: Will West Coast regroup or start to tumble?

If you thought a quiet week in the AFL was in store after the drama of Round 20 then think again as there's a number of crunch clashes that are set to play a significant role in shaping the final eight.

Games don't come much greater than Hawthorn vs. Geelong (just look back to Round 2's epic encounter if you need proof) and another loss for the Cats could rule them out of September action. However, a win for the Hawks and the top four starts to look very realistic.

Port Adelaide and West Coast meet in what has all the makings of yet another Adelaide Oval thriller before the Giants and Crows -- who simply must win to stay alive in 2018 -- take centre stage.

Get ready for another enjoyable ride. Here's What To Watch For in Round 21.

Can West Coast keep it together after Gaff loss?

Andrew Gaff's sickening off the ball hit on Fremantle's Andrew Brayshaw could spell the beginning of the end for the West Coast Eagles in 2018.

Gaff's momentary brain lapse -- which left the 18-year-old Docker with three displaced teeth and a broken jaw -- was adjudicated to be worthy of a severe eight week suspension, meaning he won't take to the field again this season.

The Eagles are already without two stars in Nic Naitanui (ACL) and Josh Kennedy (fractured leg), and with Gaff set to miss the final three home and away games of the season plus finals, the club's character is set to be tested.

To their credit, West Coast managed to regroup after Naitanui suffered his season-ending injury in Round 17 against Collingwood. The Eagles won that game before knocking off the Western Bulldogs and Fremantle last weekend.

However, they face a far greater challenge this week; Port Adelaide at the Adelaide Oval. After losing a nail-biting Showdown, the Power are almost at breaking point and must return to the winners' list this weekend. Add in the fact that West Coast dumped Port from the 2017 finals with a Luke Shuey after-the-siren goal and there's plenty of incentive for Ken Hinkley's side.

West Coast may sit in second place on the AFL ladder and enjoy a six point buffer over the third-placed Giants but a loss to Port would make a few players very anxious ahead of a crunch Round 22 game against Melbourne.

Will they fall or can the regroup again?

Can the Hawks and Cats produce another classic?

It's not quite the glory days of earlier this decade -- when these two clubs were facing off for a top-two spot, or in crucial final deep in September -- but the implications of this matchup between Hawthorn and Geelong are huge, whichever way you want to spin it.

The Hawks currently sit fifth on the ladder, and the Cats are just outside the eight in ninth, but just one win separates the two - paving the way for a blockbuster reminiscent of the early 2010s.

Put simply, if the Hawks win they're almost certain to feature in September and top four isn't out of the question, while if the Cats win, the finals race remains wide open for yet another week.

The midfield battle is one of keen interest heading into Saturday afternoon's clash; with Tom Mitchell in Brownlow-winning form and Jaeger O'Meara coming along in leaps and bounds in recent weeks, Geelong's largely unaccountable midfield might need to put some serious work into Hawthorn's dynamic duo if they're to gain the upper hand.

Tom Hawkins will be hoping to bounce back strongly from last week's one-goal game, and he might need to considering Hawks Jack Gunston and Luke Breust are in All-Australian form up the other end.

Three of the last four clashes between these sides have been decided by three points or less, so we could be in for another cracking contest come Saturday at the MCG.

Can the Demons claim a big scalp ... or will they get the jitters?

It sounds a bit alarmist to suggest a team sitting fourth on the ladder with the second best percentage in the league is vulnerable to missing finals with three rounds remaining, but that's the situation facing Melbourne.

The Demons have notched wins against Gold Coast and Adelaide in recent weeks but are yet to beat a team currently inside the top eight, meaning Sunday's clash against the equally desperate Sydney Swans at the MCG will be crucial not only for their finals hopes, but their confidence to be able to beat the best if they do go on to reach September.

A loss could be disastrous considering just four points separate the Demons from 10th-placed North Melbourne, with the Dees facing a brutal final fortnight in West Coast (away) and GWS (home). If they succumb to the Swans, it will no doubt revive memories of the final-round calamity last season when the Demons lost to Collingwood and fell short of making finals by just 0.5 per cent.

It all points to a huge clash on Sunday with so much on the line for both clubs.

The Swans are coming off a stirring, last-minute win against Collingwood and have the hard-nosed finals experience needed to stand up in these big moments - something Melbourne does not.

While the suddenly free-moving Lance Franklin looms as the wildcard for Sydney, Melbourne needs to dominate through the midfield to stop the Swans' delivery to their danger man. The Dees are ranked No.1 in the AFL for contested possessions and centre clearances, meaning they should have the midfield power needed for victory.

Melbourne co-captain Nathan Jones has stated he's daring to dream of a long-awaited finals return but if he and his teammates can't get the job done against the Swans, a repeat of last year's heartache could be on the cards.