Chicago Cardinals

In 1947, the Cardinals captured their second (and only undisputed) NFL title, then lost in a blizzard in the following year's championship clash at Philadelphia. On February 3, 1949, Parker and Phil Handler were named co-head coaches of the Cardinals, replacing Jimmy Conzelman, who had left to work for a local advertising agency. The unique arrangement, which had Parker handling the offense and Handler the defense, quickly proved to be unworkable, and Handler was returned to the front office on October 25 with the Cardinals sporting a 2–4 record.

In the season's final six games, Parker's team won four games, but a 52–20 loss to the crosstown Bears was quickly followed by Parker's surprising resignation on December 11. Publicly he stated, "I'm tired of being a head coach. The duties are too demanding", but Parker also reportedly was upset with his uncertain job status.

Detroit Lions

Parker on 1952 Bowman card

After first reconsidering his abrupt departure, Parker then signed as backfield coach of the Lions on January 21, 1950. However, after head coach Bo McMillin found himself in continuous battles with players during the ensuing campaign, he resigned on December 19, with Parker being promoted to the top job the following day.

Parker and quarterback Bobby Layne would popularize what became known as the two-minute offense, which allowed a team's offense to quickly move down the field late in a game. In Parker's first year, he led the team to a 7–4–1 record, good for a second place tie in the Western Conference. While the record was slightly better than average, he began bringing in the talent that would turn the team into a dominant force over the next few years.

Parker's superstitions also became legendary, with none of his players ever wearing the number 13, and the team always staying at the Chicago Hilton hotel when playing either the Bears or Cardinals. That choice of lodging changed after the team was placed one year on the 13th floor and lost.

In 1952, the Lions defeated the Los Angeles Rams in a divisional tiebreaker playoff on December 21, then used a strong defensive effort to defeat the injury-plagued Cleveland Browns 17–7 on the road in the championship game. In 1953, the two teams again met for in the title game, with some late heroics by Layne and Jim Doran to squeeze out a 17–16 thriller in the December 27.

Putting together a 9–2–1 mark in 1954, the Lions and Browns met for the third straight year, but this time, Cleveland battered Detroit 56–10. The after-effects of the result lasted throughout the following year, when retirement and injuries plunged the Lions to a 3–9 last-place finish. Parker was able to make another run for the title in 1956, but the Lions dropped the season finale to the Bears, the key play coming when Layne was knocked out of the game with a concussion from a hit behind the play that Parker felt was both cheap and illegal.

On July 26, 1957, Parker obtained quarterback Tobin Rote from Green Bay, a prescient move that would help the team when Layne broke his ankle and Rote then led the Lions to their third championship in six years. However, Parker was not around to enjoy the championship season after stunning the football world by resigning on August 12 during the team's preseason training camp dinner. In front of a large audience which expected him to deliver a keynote speech, Parker instead informed the audience that he was quitting.^[2][3] longtime assistant coach George Wilson was promoted the following day.^[4][5] George Plimpton wrote of this incident in his 1966 best-seller Paper Lion. In his resignation Parker cited an inability to control his players, but his struggle in obtaining a two-year contract from Lions' management also likely played a role. As of 2021, Parker is the last Lions head coach to get another head coaching job in the NFL.

Pittsburgh Steelers

After first reports had him replacing Baltimore Colts head coach Weeb Ewbank, Parker became the head coach of the Steelers on August 27, signing a five-year contract.^[6][7] During his first season, Parker led the team to a 6–6 mark and began making countless trades that left the team with few top draft choices over the next six years.

During the 1958 preseason, Parker attempted to get the players' attention by cutting five veterans, including Billy Wells, the team's leading rusher the previous season. He also reunited with Layne, trading for the signal caller on October 6. The price (quarterback Earl Morrall and two first round draft picks) was steep, but the immediate impact was evident: Pittsburgh improved to 7–4–1, their best record in a decade.

The next two years, the Steelers managed to compete at a .500 level, but dropped to 6–8 in 1961. The next year, the team finished second in the Eastern Conference with a 9–5 mark. During the latter year, the team challenged despite the retirement of Layne and the tragic off-season death of Eugene "Big Daddy" Lipscomb.

The aging team then began a decline that continued until the arrival of Chuck Noll in 1969. Pittsburgh finished 5–9 in 1964, and Parker signed a three-year deal on January 22, 1965, saying that the team was not that far away from a championship. He would change his mind when the team dropped its first four exhibition games, and repeated history by resigning on September 5, reportedly telling team owner Art Rooney, "I can't win with this bunch of stiffs."