An “armchair quarterback” is someone who follows a football game from the comforts of home. An armchair quarterback can question the decisions of the game’s actual quarterback, away from the intensity of the playing field. The term “armchair quarterback” is often used as an idiomatic expression for a military decision made far away from the battlefield, or for a business decision made in a corporate office far away from the company’s main operations.
 
“Arm-chair quarterbacking sessions” was cited in print on November 21, 1934. “Arm-chair quarterbacking” and “arm-chair quarterback” were cited in print on November 20, 1934. The first citations refer to listening to the football game on the radio; today’s armchair quarterbacks have video.
 
Another “armchair” term is “armchair isolationism.”
   
 
(Oxford English Dictionary)
armchair quarterback  n. N. Amer. colloq. (depreciative) a person who advises or offers an opinion on something (esp. a sporting event) in which he or she is not actively involved, or about which he or she lacks first-hand or specialist knowledge (cf. sense Compounds).
1940   Los Angeles Times 13 May ii. 4/3   The folks back home know that pilots know more about flying than the armchair quarterbacks in Washington.
2006   Brandweek 30 Oct. 18/1   Since the beginning of sports on TV, there have been armchair quarterbacks who feel they know what to do better than the coach or general manager.
 
armchair quarterbacking  n. N. Amer. colloq. the action or fact of being an armchair quarterback.
1952   Newport (Rhode Island) Daily News 25 July 4/2   Friends said he had done a good deal of armchair quarterbacking as he watched telecasts of last night’s hectic convention session.
     
Google News Archive
21 November 1934, Spokane (WA) Daily Chronicle, “It’s Like This,” pg. 12, col. 2:
A little pleasant task of digging into the vital details of what happened since September brings up all kinds of debating material for arm-chair quarterbacking sessions between now and the whistle starting the Washington-Washington State game Saturday afternoon.
 
30 November 1934, Corona (CA) Courier, “The Commentator” by L. M. H., pg. 4, col. 3:
THE powers-that-be of the football firmament threaten to destroy one of the country’s most popular indoor sports—arm-chair quarterbacking—at one single merciless stroke. The claim has been brought forth that the much-lamented decrease in gate receipts at the stadiums is due in no small measure to the great army of fans who “prefer” to sit by their radios in the comfort of their homes and listen to the play-by-play broadcasts, instead of pouring out by the thousands to occupy the seats of the huge bowls at two and three whackers a throw.
(...)
Speaking as an old-time arm-chair quarterback there’s nothing we like better than to follow our favorites with pencil and chart and our ear glued to the speaker—unless it’s being right there in the thick of the howling mob using our eyes instead of our ears.
 
Google News Archive
7 December 1938, Montreal (Quebec) Gazette, “Pro-Gascon Shift Noted In Campaign” by Stanley Goldner, pg. 13, col. 2:
The armchair quarterbacks cast an eye on the contrasting personalities of both men, on the is sues of the campaign (what there were of them) and on the electorate, and the way things doped out the ex-mayor had only to say “Boo!” to flatten all opposition in sight.
 
7 December 1940, Springfield (MA) Daily Republican, “Radio Today,” pg. 8, col. 1:
Lovers of Classical Music Score
Over Grid Fans Today
Morning, Afternoon and Evening Performances Available—But Armchair Quarterbacks Can Hear Rice-Southern Methodist, Notre Dame-S. C.
 
3 September 1947, Christian Science Monitor, “College-Pro All-Star Game Ends Careers of Two Greats,” pg. 12:
So while tonight s game will probably not prove anything too conclusive, it will nevertheless offer an interesting test-and provide the armchair quarterbacks with some fuel for argument.
 
Google News Archive
12 October 1951, Lewiston Daily Sun, “Monopoly In Sports” (editorial), pg. 4, col. 1:
But does this privilege Include every armchair quarterback too lazy or too stingy to put a personal appearance al the scene of the contest?
     
OCLC WorldCat record
Bart Starr tells how to be an armchair quarterback.
Author: Bart Starr; National Football League.
Publisher: [New York : North American Philips Co., 1966]
Edition/Format: Book : English : National Football League authorized ed
 
OCLC WorldCat record 
NFL 1968 line up : see it best on GE color TV : General Electric TV viewer armchair quarterback : here’s the TV 1969 line-up of features.
Author: Bart Starr; General Electric Company.
Publisher: [Appleton, Wis. : R.H. Lewis Co., 1968]
Edition/Format: Book : English
   
OCLC WorldCat record 
The Armchair quarterback
Author: John Thorn; David Reuther
Publisher: New York : Scribner’s, ©1982.
Series: The Armchair library
Edition/Format: Book : English
   
OCLC WorldCat record
The armchair quarterback playbook : the ultimate guide to watching football
Author: Christopher Lee Barish
Publisher:San Francisco, Calif. : Chronicle Books, ©2007.
Edition/Format: eBook : Document : English