This is because, during eras before overtime was introduced to American football, leagues generally ignored tied games when calculating winning percentage.
This was common in the NFL's early years as scheduling was not standardized and teams entered and left the league regularly.
The 1991 inaugural season of the World League of American Football saw the Raleigh-Durham Skyhawks fold after losing all ten of their regular-season games.
The following year, the WLAF replaced that franchise with the Ohio Glory who almost met the same fate but managed one win in their lone season.
The 1938 Clintonville Four Wheel Drive Truckers failed to score a point in a nine-game season but managed two 0–0 ties.
Imperfect seasons were common in the Canadian football during the first half of the twentieth century when fewer games were played and more leagues were challenging for the Grey Cup.
The Los Angeles Reign lost all ten games it played during the league's (and team's) three-year existence.
The Atlantic City Seagulls of the (now defunct) summertime, minor league USBL finished the 2001 season with an 0–28 record.
No team has ever come close to losing every game in an NHL season; the worst record is by the 1974–75 Washington Capitals who went 8–67–5 (8 wins, 67 losses, 5 ties).
The sabermetric baseball statistic Wins Above Replacement is calculated on the premise that even a team consisting entirely of replacement-level players, (i.e., a player that could be "replaced" by a call-up from the minor leagues without any significant statistical difference) is expected to win a baseline minimum number of games (typically 40–50, depending primarily on the caliber of the team's division) per 162-game season.
With a win percentage of .130, the Spiders are (as of 2020) the last of three major league teams to have finished a season below the Mendoza line (.200) in win percentage for a minimum of 120 games; the others were the 1889 Louisville Colonels (.196), and the 1890 Pittsburgh Alleghenys (.169), whose best players had jumped to the Pittsburgh Burghers of the newly formed Player's League.
Since the establishment of the American League in 1901, the teams to have come closest to a perfectly winless season are the Philadelphia Athletics in 1916 (36–117), the Boston Braves in 1935 (38–115), the New York Mets in their 1962 inaugural season (40–120), the Detroit Tigers in 2003 (43–119), the Baltimore Orioles in 2018 (47–115), the Detroit Tigers in 2019 (47–114), the Oakland Athletics in 2023 (50–112), and the Chicago White Sox in 2024 (41–121).
In 2016, Grêmio Barueri lost all 19 matches of the Campeonato Paulista Série A3, the third level of the São Paulo state championship.
In top-level domestic league football, however, a handful of teams have completed their respective seasons without winning a game.
In the 1999–2000 Vyshcha Liha, the highest division of Ukrainian football championship, FC Zirka Kirovohrad tied 9 matches and lost 21 out of 30.
In the 2018 Úrvalsdeild, the highest division in Icelandic football championship, Knattspyrnudeild Keflavík drew 4 games and lost 18 out of 22.
In the 2018–19 Campionato Sammarinese di Calcio, the football championship in San Marino, Virtus drew 2 games and lost 17 out of 19.
The West Australian Football League has existed within Western Australia under various names since 1885, and until the 1980s was of equivalent standard to the VFL and SANFL.
From the time of the formation of the Victorian Football League in 1896 until it was dissolved in 1995, the VFA was the second-tier club competition in Victoria.
Before the 1880s, they were generally less than ten matches in length and some "first-class" counties played only against one or two different opponents, so that a team losing all its games was not uncommon.
However, because of the development and popularity of one-day cricket, seasons have been reduced to twenty-four games in 1969 and twenty in 1972, though this was increased by two in 1977 and 1983.
Also, because of improvements to pitches via the heavy roller and covering to protect from rain, the proportion of games "drawn" (not finished) has steadily risen since the 1870s.
With the exception of the Sheffield Shield since the 1970s, most first-class cricket competitions outside England have either been knock-outs or of such short length that it becomes an everyday occurrence for a team to lose all its games.
The longest series belongs to HK Dniprovski Vovky who lost all 30 games in the regulation time in the 2007–08 season.
In addition, they were on the receiving end of Rugby League's largest ever defeat – a 144–0 loss to York City Knights.
The Brisbane Rugby League premiership began in 1909 and continued in varying forms until 1996, after which it was superseded by the Queensland Cup.
Super Rugby, the Southern Hemisphere's principal club competition, has seen two teams go through an entire season with no wins or draws.
In 2018, the Sydney Rays finished the National Rugby Championship regular season with 0 wins and 0 draws in 7 games.
In 2019, the Austin Elite finished the Major League Rugby regular season with 0 wins and draws in 16 games.
In many sports winless seasons may be the norm for many, or even most, competitors; particularly those where the competition does not take place in the form of discrete 1-on-1 matches, such as running.