Just checked WPA: Win Percentage Added.  Only 95 times has a player had over 1 for that (IE: added enough on their own to account for a win and then some but his teammates didn't do so good).

1. Jose Bautista: 2013-05-22 going 4 for 4 with 2 HR, 1 walk, 1 stolen base.  Home run in the 4th to tie the game, walk & SB in a tie game in the 6th, home run to tie it in the 9th, a two out single to win it in the 10th
2. Roberto Alomar: 1991-05-10 going 3 for 4 with 2 HR, and 2 BB.  2 out HR to tie it in the 9th, 1 out HR to win it in the 11th.
   
3. Kelly Gruber: 1989-06-12 going 5 for 6: 2 out double to win it in the 11th (Jays losing by 1 before that)
4. Paul Molitor: 1993-05-13 going 2 for 5: Home run in the 6th to move the Jays ahead 2-1, 2 out 2 run double in the bottom of the 9th to win it (trailing by 1 ahead of that)

Well, each win is worth 1.0 so I see a guy going over 1 as a pretty crazy thing.  0.5 happens a lot more often (obviously) but this is a fun way to see some of the biggest impacts of players in a single game. 

193 times pitchers for the Jays have had a 0.5 or greater WPA, never at 1.0 though.

Just hit me, great opportunity to get WAR leaders by position for the Jays...

• Starting Pitcher
•  Roger Clemens 1997 11.9 (won pitchers triple crown)
• Pat Hentgen 1996 8.6 (Cy Young)
  
• Roy Halladay 2003 8.1 (Cy Young)
• Roger Clemens 1998 8.1 (won pitchers triple crown)
• Dave Stieb 1984 7.9 (two closers came in 1/2 for Cy that year, Stieb was 7th)
• Dave Stieb 1982 7.6 (4th in Cy despite far more innings, lower ERA, more K's, fewer walks, but 1 less win than the guy who got it)
• Jimmy Key 1987 7.4 (2nd in Cy, first not to lead league in pitchers WAR)
• Relief pitcher (all the guys with 3.0+ WAR)
  
• Mark Eichhorn 1986 7.3 (157 IP, 1.72 ERA, 166 K's)
• B.J. Ryan 2006 3.6 (38 saves 1.37 ERA)
• Tom Henke 1989 3.4 (20 saves, 89 IP 1.92 ERA)
• Jerry Garvin 1980 3.4 (2.20 ERA just 8 saves)
• Tom Henke 1987 3.3 (0 wins, 34 saves)
• Paul Quantrill 1997 3.2 (5 saves, 88 IP 1.94 ERA)
• Duane Ward 1992 3.1 (12 saves setting up Henke)
• Duane Ward 1993 3.0 (45 saves)
• Tom Henke 1990 3.0 (32 saves)

Positions require 81 games at that position to qualify.  Top 3 per position... WAR is at that position only

• CA
• Gregg Zaun 2005 3.6
  
• Ernie Whitt 1983 3.4
  
• Russell Martin 2015 3.2
  
• 1B
• John Olerud 1993 7.8
• Carlos Delgado 2000 7.3
• Fred McGriff 1989 6.6
• 2B
• Roberto Alomar 1992 6.6
• Roberto Alomar 1993 6.1
• Aaron Hill 2009 5.8 (4th is his 2007 season)
• 3B
• Josh Donaldson 2016 7.2
• Josh Donaldson 2015 7.1 MVP (his 2017 is 5th)
  
• Kelly Gruber 1988 5.2 (his 1987 is 4th)
• Note: Scott Rolen 2009 was 3.9 in just 88 games and 3.4 in 2008 in just 115 games
• SS
• Marco Scutaro 2009 5.4
  
• Tony Fernandez 1987 5.1
• Tony Fernandez 1986 5.0 (5th through 8th are all Fernandez too)
• Yunel Escobar 2011 4.8
  
• LF
• Reed Johnson 2006 5.1
• Shannon Stewart 2000 5.0
• George Bell 1987 5.0 MVP (his 1985 is 4th)
• CF
• Lloyd Moseby 1984 7.3
  
• Devon White 1993 6.3
• Devon White 1991 6.3
• Vernon Wells 2006 6.2 (I knew some would wonder where this ranked)
• RF
• Jose Bautista 2011 8.3
• Jesse Barfield 1986 7.6
• Jose Bautista 2010 7.0
• DH
• Paul Molitor 1993 5.6
• Edwin Encarnacion 2012 5.0
• Edwin Encarnacion 2015 4.9 (4th is his 2016 season, followed by Winfield's 1992)
• PH/R at least 50% of the time
• Rance Mulliniks 1990 0.7
• Anthony Alford 2017 0.2
• Darrell Ceciliani 2017 0.2

For top rookies by position...

Me either - that was a surprise when I pulled the stats.  Fernandez dominating otherwise wasn't a shock, although I expected Tulo and someone else to be up there.

Scutaro in his big year hit 282/379/409 for a 108 OPS+ and had 2.0 dWAR that year (a drop from his 2.7 the year before).  Funny he was only here 2 years but did very well.  Then went to Boston and made over $10 mil over 2 years, $6 mil from Colorado, then got a killer deal from SF 3 years over $20 mil which they regretted.  He was an All-Star the first full year in SF then played just 5 more games due to back problems.  A shame as his career was going so well in his mid 30's.  With Oakland he was a meh utility guy who had an OPS+ under 90 then with the Jays at 33 he had a 108 OPS+ and was off to the races.  From that 2nd year here to the end of his career he had a 102 OPS+ over 695 games.  26-32 he just had a 87 OPS+ over 696 games.  Weird to have a big jump up at 33 - most have a bigger drop.  This was well after Canseco & Clemens were here so they had nothing to do with it, plus by then testing was in place so he was probably clean and it was just an amazing thing.

Good point Mike.  Got me thinking about defense so before PI is closed by BR and they start charging for it again...

Top defensive WAR by Jay players ever...

John, I am pretty sure that the outfielder arm stats in the mid 80s were pretty rudimentary.  Barfield not only led the league in assists, but baserunners rarely tested his arm and that part of it, I think, was missed.  He had good range too when he was young. Rios' 2008 was a year in which he played 820 innings in right field and 522 innings in centerfield.  He was, of course, a fully capable defensive centerfielder and his dWAR reflects that- he didn't get as many fielding runs as Barfield in his best year, but he took less of a hit for position.

There's little doubt in mind that Barfield was the better right-fielder and Rios the better centerfielder of the two. 

Good point on the difficulty of defensive stats over time - in the 80's much more limited than in the 00's or today.  I bet White would be even more amazing if they had the trajectory and how hard hit balls were back then.  I know the advanced stats in the 80's/90's were very limited (innings instead of games played was the big help then, some estimated balls to a side based on various methods but human error was a big factor when Stats Inc started tracking where balls were hit and how hard - I could've been tracking that stuff but chose not to as I knew I'd miss a lot doing it via TV in the days before PVR, plus the pay was well below $10 an hour iirc).  Alomar is still listed as a negative on defense for most of his prime years (93/94/95 ages 25/26/27) which doesn't pass the eyeball test. 

Barfield seemed to range far and wide and had that killer arm back in the 80's yet never got to 2 wins on defense which again makes zero sense - often those assists were of the toss out at the plate types (removing a run and adding an out) which should be massive pluses.  In 1987 they give him 8 defensive runs saved by his arm - on 16 assists, checking game logs Barfield tossed out 7 at home, 6 at 2B, 2 at 3B (1 was trying to score ran back but not in time, other was an error on the 3B on a Barfield throw), 1 at 1B.  So 7 runs directly saved, an 8th as well for all intents and purposes (each changing a run into an out) and that isn't factoring in how often runners stopped at 3B or the other 8 guys thrown out on the bases.  Yeah, he deserved a lot more credit back then than he got.