Vinny Testaverde has the highest completion percentage by a quarterback in a game with 20+ completions versus the Rams, at 91.3 percent on December 26, 1993.

highest completion percentage by quarterback with at least 20 completions in a game vs rams
Interpreted as:
highest completion percentage by quarterback with at least 20 completions in a regular-season game vs rams
12/26/1993Testaverde10/26/2014Smith9/20/2015Cousins9/15/2002Collins12/8/2013Palmer9/27/2015Roethlisberger11/23/2014Rivers10/25/2015McCown11/28/1993Young10/21/2012Rodgers11/22/1998Beuerlein9/18/1994Young12/21/2014Manning9/13/2015Wilson11/27/2016Brees9/19/1993Simms11/11/1984Fuller12/16/2018Foles9/15/2013Ryan11/23/1997Collins11/24/2013McCown9/11/1994George12/9/2012Fitzpatrick91.386.285.284.684.483.382.981.381.381.180.879.578.178.077.877.877.877.476.776.776.676.375.8
NAMEDATETMOPPPCTCMPATTYDSAVGTDTD%INTINT%SCKSCKYRATE
Vinny TestaverdeVinny Testaverde12/26/1993CLECLE@ RAM
@
91.321232169.428.700.013134.8
Alex SmithAlex Smith10/26/2014KCKCvs. STL
vs.
86.225292237.700.000.02898.7
Kirk CousinsKirk Cousins9/20/2015WASWASvs. STL
vs.
85.223272037.513.700.0212110.3
Kerry CollinsKerry Collins9/15/2002NYGNYG@ STL
@
84.6222630711.813.813.8216112.7
Carson PalmerCarson Palmer12/8/2013ARIARIvs. STL
vs.
84.427322698.413.100.017112.1
Ben RoethlisbergerBen Roethlisberger9/27/2015PITPIT@ STL
@
83.320241928.000.014.232282.6
Philip RiversPhilip Rivers11/23/2014SDSDvs. STL
vs.
82.929352918.312.912.93998.9
Josh McCownJosh McCown10/25/2015CLECLE@ STL
@
81.326322708.400.000.0415101.8
Steve YoungSteve Young11/28/1993SFSF@ RAM
@
81.3263246214.4412.513.1310145.3
Aaron RodgersAaron Rodgers10/21/2012GBGB@ STL
@
81.130373429.238.100.0310132.2
Steve BeuerleinSteve Beuerlein11/22/1998CARCAR@ STL
@
80.821262118.127.713.8527110.1
Steve YoungSteve Young9/18/1994SFSF@ RAM
@
79.531393559.125.100.026121.7
Eli ManningEli Manning12/21/2014NYGNYG@ STL
@
78.1253239112.239.400.015148.8
Russell WilsonRussell Wilson9/13/2015SEASEA@ STL
@
78.032412516.112.412.463290.1
Drew BreesDrew Brees11/27/2016NONOvs. LA
vs.
77.828363108.6411.100.0214139.6
Phil SimmsPhil Simms9/19/1993NYGNYGvs. RAM
vs.
77.821272178.000.000.0533100.2
Steve FullerSteve Fuller11/11/1984CHICHI@ RAM
@
77.821272408.900.000.0213103.7
Nick FolesNick Foles12/16/2018PHIPHI@ LAR
@
77.424312708.700.013.20089.4
Matt RyanMatt Ryan9/15/2013ATLATLvs. STL
vs.
76.733433748.724.700.0217117.8
Kerry CollinsKerry Collins11/23/1997CARCAR@ STL
@
76.723302869.513.300.0432116.8
Josh McCownJosh McCown11/24/2013CHICHI@ STL
@
76.636473527.524.312.118102.4
Jeff GeorgeJeff George9/11/1994ATLATLvs. RAM
vs.
76.329382877.637.900.000123.5
Ryan FitzpatrickRyan Fitzpatrick12/9/2012BUFBUFvs. STL
vs.
75.825332477.513.013.052793.9
Colin KaepernickColin Kaepernick12/24/2016SFSF@ LA
@
75.728372667.225.412.7413101.9
Matthew StaffordMatthew Stafford10/16/2016DETDETvs. LA
vs.
74.223312708.7412.900.015139.8
Results may be incomplete. StatMuse has complete game-level data for completion percentage and completions going back to the 1950 season.

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