UEFA has confirmed that Manchester United's Champions League quarterfinal tie could be reversed if they are drawn at home in the same matchweek as Manchester City.
Both Manchester clubs progressed to the last eight of the competition, but UEFA regulations do not allow two teams in the same city to play on the same day, nor on consecutive nights.
If both clubs are drawn in the same home and away sequence in Friday's draw (11am UK, 7am ET), ], it will be United's fixture that will be changed because they finished behind champions City in their domestic competition last season.
"Following a decision made by relevant local authorities, Manchester City and Manchester United cannot play at home on the same night, nor on consecutive nights," UEFA said.
"Should both clubs be drawn within the same sequence [home or away], the team having finished lower in the domestic league the previous season -- in this case United - will be reversed in accordance with the UEFA Club Competitions Committee principles.
"In accordance with paragraph 21.01(b) of the UEFA Champions League regulations, the UEFA administration will determine which matches will be played on Tuesday, which matches on Wednesday."
There could also be another fixture reversal for Ole Gunnar Solskjaer's team if both United and City progress through to the semifinal stage of the competition.
The two Manchester clubs were also hit by the regulation in 2011-12, when both were drawn at home in the second leg of their round-of-32 Europa League ties. However, rather than flipping a fixture, UEFA moved City's game at home to Porto to the Wednesday while United faced Ajax the following night. United had won the title the previous season, with City in third, but both clubs dropped into the Europa League from the Champions League group stage.
In the Europa League round of 16 draw, both Arsenal and Chelsea were drawn at home but UEFA ruled to reschedule Arsenal's first-leg tie against Rennes as Chelsea won the FA Cup.
It's not the first time this season both clubs have been affected with fixture rescheduling with the date for the Manchester derby moved to April 24 due to both sides progressing to the FA Cup quarterfinals.
United secured their place in the Champions League quarterfinals with a stunning 3-1 win over Paris-Saint Germain at the Parc des Princes to go through on away goals whilst City strolled to a 10-2 aggregate victory against Schalke.
The Champions League draw for the quarterifnals and semifinals takes place on Friday with the Premier League boasting four teams for the first time since 2009.