Even when it came to players picked up on AFL national draft day, how long was sufficient enough time to pass judgment on a player's worth against the selection with which he'd been taken?

That business is even harder now given the advent of the trading of picks, exchanges involving future picks and bids on players from football academies, plus the advent of free agency and the capacity to also list delisted free agents.

One constant in the ever-changing player marketplace, though, remains the instant gratification delivered via the trade table. While what's been given up to acquire a player may remain the subject of vigorous debate, supporters are better placed to give a thumbs up or down on those brought into their club with whose names they are already familiar.

Nearly 40 established AFL players changed clubs last trade period. Some, like former champion Hawthorn pair Sam Mitchell and Jordan Lewis in a blaze of publicity, others, such as former GWS second-round draft pick Pat McKenna, who headed to Melbourne, barely raising a flicker of recognition.

Approaching the halfway mark of the season, who among that group have been the hits, and who, for whatever reasons, the misses? Which clubs have got it right or wrong thus far? Or perhaps had a taste of both.

Hawthorn are a good example of the latter. The Hawks took an enormous gamble letting veterans Mitchell and Lewis go, a move many still question. And the fortunes of their trade-ins have provided plenty of contrast.

For all the ripples, the Hawks in 2017 still have a gun midfielder called Mitchell leading the way. Just one with a different first name.

The former Swan Tom Mitchell has clearly been the pick of the trade-ins to date, his average 34.1 disposals a game ranking him No.1 in the AFL among the ball-winners, ranked sixth in the competition for contested possession and tackles, seventh for uncontested possession.

Mitchell has had fewer than 30 disposals in just one of his eight games, and he still managed to pick up 27 in that one. The delivery still may not be quite as crisp as that of his namesake, but no-one could argue that the former Sydney midfielder hasn't done all that's been asked and then some.

His new Hawk teammate Jaeger O'Meara was winning enough of the ball early without necessarily having much impact. But a knee injury has kept the former Sun star out of all but one of the past five games, and he doesn't look like returning soon.

Ricky Henderson was signed as a delisted free agent but if former Tiger Ty Vickery, signed as a free agent, is to be of any use to a recast Hawthorn, he'd want to get a wriggle on.

Vickery had little impact either up forward or in the ruck in his first two games in brown-and-gold against Essendon and Adelaide, and his third, against Gold Coast, was a nightmare, only a back injury saving him from the selection axe.

Since then he's had three games in the VFL with Box Hill in which he's performed well. With the Hawks hit by injury he gets another chance in the seniors this weekend against Collingwood.

Hawthorn, via Mitchell, can at least claim some success on the trade front. Which might be more than their opponent on Saturday.

The Magpies brought in Daniel Wells, Chris Mayne (both free agents), Will Hoskin-Elliott and Lynden Dunn to the mix for 2017. Out of a possible 32 collective games, that quartet have played a total of 17, with Hoskin-Elliott the only one to play more than three.

He was handy in round two with three goals against Richmond, but has been patchy since. Wells' silky disposal has given the Pies what they lack, but it's only been available in three games due to a pre-season calf injury. Dunn was handy against Geelong's Tom Hawkins but hadn't been picked prior to that round six clash.

Mayne, meanwhile, continues to ruffle Pie fans' feathers with little return on a $500,000-a-year salary. Mayne made Collingwood's round one team only as a late inclusion, did little in the next two games before being dropped, and has been only fair in four games in the reserves.

The two West Australian clubs have done well out of Hawthorn, Mitchell for West Coast, and another premiership Hawk in Brad Hill beginning to look very ominous for Fremantle. But some of the best performers on the trade front have been those without the bigger reputations, Richmond's trio of trade recruits underlining that.

While one of the biggest names in last year's trades, Brett Deledio, left the Tigers for GWS but is still yet to play a game after a pre-season calf injury, three more tradees - Dion Prestia, Josh Caddy and Toby Nankervis - arrived at Punt Road.

It was the first pair which had clearly the bigger reputations, but while Caddy has battled poor form and Prestia had only middling form before injuring a hamstring, ruckman Nankervis has been a revelation.

With only a dozen AFL games to his name, Nankervis has given the Tigers real big-man presence, aggressive at the ruck contest and around the ground, competitive even against the likes of Sam Jacobs and Aaron Sandilands.

And three more "middling" trades in terms of profile but unmitigated successes must surely be Zach Tuohy at Geelong, Jack Steele at St Kilda and Carlton's Caleb Marchbank.

The Irishman Tuohy has provided the Cats with a ton of drive from half-back, his average 26 disposals easily the best figure of his seven-year career. Steele, another Giant squeezed out by a glut of talent, is equal sixth in the AFL for tackles. And Marchbank looks a definite long-term bet for the Blues in a key defence post, where he's played smart football. He's particularly good on the intercept.

Marchbank seems destined to become a big name. Those who already were when they were traded last summer are mostly the subject of "ifs" or "buts" - for Deledio and Travis Cloke, now at the Bulldogs, those "ifs" relate to injury, and for Melbourne's Jordan Lewis, whose form has been sound in the games he has played, the considerable "but" a costly three-game suspension.

Those fortunes could still change for the better, with Cloke back on deck for the Dogs on Friday night after missing a month with broken ribs, Deledio having set his sights on a round 14 debut with the Giants.

Their football will need to be outstanding over the back end of the season, however, for the ledger in those clubs' supporters' minds to be better balanced between expectation and reality. The trade table is still the one source of recruiting in which the thumbs up or down is, by comparison, a relatively straightforward call.

ROHAN CONNOLLY'S PICK OF THE TRADE CROP

1. Tom Mitchell (Hawthorn)

2. Zach Tuohy (Geelong)

3. Caleb Marchbank (Carlton)

4. Brad Hill (Fremantle)

5. Jack Steele (St Kilda)

6. Toby Nankervis (Richmond)

7. Sam Mitchell (West Coast)

8. Nathan Hrovat (North Melbourne)

9. Jarrod Witts (Gold Coast)

10. Marley Williams (North Melbourne)

THE TRADE-INS

(Signings by trade or free agency, not including delisted free agents)

ADELAIDE: nil.

BRISBANE LIONS: Jack Frost (Collingwood).

CARLTON: ???Billie Smedts (Geelong), Caleb Marchbank (GWS), Jarrod Pickett (GWS), Rhys Palmer (GWS).

COLLINGWOOD: Daniel Wells (North Melbourne - free agent), Chris Mayne (Fremantle - free agent), Will Hoskin-Elliott (GWS), Lynden Dunn (Melbourne).

ESSENDON: James Stewart (GWS).

FREMANTLE: Cam McCarthy (GWS), Joel Hamling (Western Bulldogs), Bradley Hill (Hawthorn), Shane Kersten (Geelong).

GEELONG: Zach Tuohy (Carlton), Aaron Black (North Melbourne).

GOLD COAST: Pearce Hanley (Brisbane Lions), Jarrod Witts (Collingwood), Jarryd Lyons (Adelaide).

GWS: Brett Deledio (Richmond).

HAWTHORN: Tom Mitchell (Sydney), Jaeger O'Meara (Gold Coast), Ty Vickery (Richmond - free agent).

MELBOURNE: Jordan Lewis (Hawthorn), Michael Hibberd (Essendon), Pat McKenna (GWS).

NORTH MELBOURNE: Paul Ahern (GWS), Nathan Hrovat (Western Bulldogs), Marley Williams (Collingwood).

PORT ADELAIDE: nil.

RICHMOND: Dion Prestia (Gold Coast), Toby Nankervis (Sydney), Josh Caddy (Geelong).

SYDNEY: nil.

ST KILDA: Jack Steele (GWS), Nathan Brown (Collingwood - free agent), Koby Stevens (St Kilda).

WEST COAST: Sam Mitchell (Hawthorn), Nathan Vardy (Geelong).

WESTERN BULLDOGS: Travis Cloke (Collingwood).