Don't know. All we know for sure is Garrett ended up exactly where he wanted to be if the Cowboys let him go....(the Giants).
And not defending Jason (or not trying to), I think talent covered his butt more than a few times. And he never had the knack for motivating the team in the win or go home games. He lacked in firing guys up expecting talent to overcome everything else.
At the same time, NFL QBs never have been the best at being NFL coaches. Jim Harbaugh is considered the exception to the rule but looking at the list.....(through 2014)
Jim Harbaugh, Bears 2011-14 49ers 40-15-1 .723
John Rauch, N.Y. Bulldogs 1966-68 Raiders, ’69-70 Bills 40-28-2 .586
Frankie Albert, 49ers 1956-58 49ers 19-16-1 .542
Jason Garrett, Cowboys 2010-14 Cowboys 35-30-0 .538
Tom Flores, Raiders 1979-87 Raiders, ’92-94 Seahawks 97-87-0 .527
Allie Sherman, Eagles 1961-68 Giants 57-51-4 .527
Ted Marchibroda, Steelers 1975-79/’92-95 Colts,’96-98 Ravens 87-98-1 .470
Gary Kubiak, Broncos 2006-13 Texans 61-64-0 .488
Sam Wyche, Bengals 1984-91 Bengals, ’92-95 Bucs 84-107-0 .440
Harry Gilmer, Commanders 1965-66 Lions 10-16-2 .393
June Jones, Falcons 1994-96 Falcons, ’98 Chargers 22-36-0 .379
Steve Spurrier, 49ers 2002-03 Commanders 12-20-0 .375
Jim Zorn, Seahawks 2008-09 Commanders 12-20-0 .375
Kay Stephenson, Bills 1983-85 Bills 10-26-0 .278
Frank Filchock, Commanders 1960-61 Broncos 7-20-1 .268
Flores won two Super Bowls, Harbaugh, Rauch and Wyche got to Super Bowls, while Sherman had three NFL title games, and Marchibroda came within a Hail Mary of going to the Super Bowl in 1995 (a little trivia final play of the 1995 AFC Championship game was a Hail Mary by Jim Harbaugh which hit Aaron Bailey in the chest and fell to the turf before he could haul it in).
Even Hall of Fame QBs haven't been successful as NFL Head Coaches.....
Sammy Baugh, Commanders 1960-61 N.Y Titans, ’64 Oilers 18-24-0 .429
Bob Waterfield, Rams 1960-62 Rams 9-24-1 .279
Norm Van Brocklin, Rams 1961-66 Vikings, ’68-74 Falcons 66-100-7 .402
Otto Graham, Browns 1966-68 Commanders 17-22-3 .440
Bart Starr, Packers 1975-83 Packers 52-76-3 .408
(If you want to add the Saints’ Sean Payton (77-43, .642), a replacement quarterback during the ’87 strike, to this list, be my guest.)