So as we head into trading season the question that comes up is what did the Jays do in other years when they contended? What did they give up, what did they get back? Did it work?
For sake of argument we'll say it worked in '85, '91, '92, '93, '15, '16, '22, '23 as they made the playoffs all those years. Super worked in '92, '93 as they won the WS those years, '15, '16 also saw them win some division series. I ignored the bizarre 2020 season (non-standard deadline, short season, so many weird things) at first, but added after a request (why not?) all deals were August 27-30th that year. I'm using July 15-August 5th as the trade deadline, but will see if other significant trades happened close to that range (July 1st to August 31st). I'll try to avoid minor leaguer for minor leaguer trades (ie: for AAAA types to fill in depth stuff).
Note: No trades in 1983 or 1984 or 1986 as all 3 years few thought the Jays still had a shot come August 1st. Pre 1994 was all Pat Gillick, 1999 + 2000 was Gord Ash dreaming in technocolor, 2006 was JPR doing a deal while 5 1/2 out, 2015 was AA's only contending year, 2016 and beyond were the current crew.
In brackets I added WAR for the team they were traded to if they had significant time elsewhere post Jays (WAR listed is post Jays or as a Jay depending on situation). So in all those years of contention and many trades the biggest losses were Jose Mesa (who didn't become good until he switched teams again), Luis Aquino, Jeff Kent (mostly after he left the Mets), Steve Karsay (again, post leaving the team he was traded to), Michael Young (the biggest loss outside of Kent), Matt Boyd, and Jesse Chavez (again mostly post team he was traded to). Mid-season trades have only really cost big time with one guy then (with what he did at the team he was traded to) and that was Michael Young by good ol' Gord Ash (no bad deal list is complete without Ash being mentioned).
Contending trades: Atkins: 20 deals, leading to 3 playoff appearances and 1 oh so close. AA: 4 deals, 1 playoff in the only year he made mid-season adds. JPR 1 deal, 0 playoffs in 1 sorta try. Ash 6 deals, 0 playoffs in 2 tries. Gillick: 14 deals, 5 playoffs, 2 WS titles, twice not making playoffs.
Going by pure WAR (not a good method) the Jays 'won' 23 of these 46 trades - better than expected given how often they were 'potential' for under 1/2 a season. I only counted WAR for the team they were traded to, or for their first 6 full years there (Michael Young) as otherwise the WAR totals would be silly for guys like Mesa, Kent & Young when they did a lot post their first 6 years. Net total WAR was 61.5 given up for 35.0 returned, resulting in 10 playoffs and 2 WS titles (both heavily impacted by trades mid-season). Looking through you can see LOTS of flops, and just a few guys who blossomed away from Toronto (Kent, Young, Mesa, Aquino, Karsay, Boyd, Jesse Chavez). A few showed hope post Toronto like Tellez but flopped shortly after that hope (sucks as I am a fan of Tellez).
If anyone can think of other trades that should count please mention it in the comments. I tried to catch everything that was July/August ignoring September trades (not qualified for playoffs) and June/earlier (too soon to count as deadline deal imo). I looked at other years just in case the team did deals to try to sneak in but didn't see anything beyond dumps (1998 and 2024 being the biggest ones). 1984/1983 were the first years in contention but Gillick didn't feel it was the right time to deal I guess (both years some relief help would've gone a long way to helping).