The hosts, knocked out of the Champions League by Real Madrid on Tuesday after a controversial red card for Nani, took a fifth-minute lead through Javier Hernandez and doubled their lead six minutes late with a Wayne Rooney free kick.
Just when United had started to think they could smell a Wembley date, Chelsea pulled one back on 59 minutes through substitute Eden Hazard before Ramires levelled nine minutes later.
The day's other quarter-final will also be replayed after Championship (second division) Millwall and Blackburn Rovers played out a 0-0 draw. Manchester City and Wigan Athletic booked their places in the semi-finals on Saturday.
- Sports & Recreation
- Javier Hernandez
- Champions League
- Wayne Rooney