Manchester United are likely to drop out of the top bracket of seeds if they return to the Champions League next season.
United, who won the last of their record 20 league titles in 2013, began the season ranked sixth in Europe under UEFA's coefficient system but have already fallen behind Atletico Madrid, the reigning Spanish champions and last season's runners-up in the Champions League.
And United, who are not playing in Europe for the first season since 1989-90, are at risk of being of being overtaken by clubs such as Premier League rivals Arsenal, Portuguese club Porto and German duo Schalke and Borussia Dortmund.
After a difficult start to Louis van Gaal's tenure as manager, United went into the current international break in the top four of the Premier League table, a position that would secure them a return to Europe's top club competition come the end of the season.
If they were not among the eight teams with the highest coefficient in next season's competition then, under current rules, they would not be top seeds when the draw for the group stage is made next August.
Under plans supported by some other clubs, including Manchester City, the seeding system could be revamped so the eight top seeds would be the defending European champions and the seven winners of each of the highest-ranked domestic European leagues.
If that was the case Van Gaal's side, who are already eight points behind leaders Chelsea, would have to win the Premier League in order to be granted seed status.
Such proposals are expected to be opposed by clubs who are accustomed to being top seeds every year under the current coefficient system.
United's current coefficient stands at 101.364 and Atletico passed it by beating Juventus on Oct. 1, moving up to sixth in the ranking kept by Europe's governing body in the process.
They will drop below eighth-placed Schalke if the Bundesliga club, whose current coefficient is 98.740, secure one more win and one more draw in this season's competition. The German club are in a group with Chelsea, Sporting Lisbon and Maribor this season.
Arsenal currently stand 10th in the rankings (Valencia, who are ninth, are another club experiencing a rare season out of Europe) but Arsene Wenger's team are almost certain to climb above United if they qualify for the knockout phase this season.
That brings a bonus of five points, while group-stage wins and draws are worth two points and one respectively.
Porto, whose current ranking is 92.209, would pass United with three more group-stage wins and qualification for the round of 16.
Meanwhile, 2013 finalists Borussia Dortmund would probably need to reach the quarterfinals to pass United, while last season's Ligue 1 winners Paris Saint-Germain could go above the three-time European champions if they are semifinalists.
There is also the possibility for clubs such as Schalke and Arsenal to overtake United if they finish third in their group but collect points, albeit at a lower rate, by progressing in the Europa League.
One possible reprieve could come for United if they return to the Champions League but clubs ranked above them do not.
Schalke are only 11th and Dortmund are 12th in the Bundesliga at the moment while Arsenal, who are eighth in the Premier League after seven matches, are also outside the Champions League places in their domestic league.
A problem for United, beginning in the 2016-17 season, is that the points they won in the 2010-11 campaign, when they reached the final, will no longer count as only those accrued in the previous five years are used in the coefficient.
That run brought United 33 points, whereas they only banked 13 in 2011-12, when they failed to get out of their group, and 18 in 2012-13, when they were eliminated in the round of 16.