Jose Mourinho made nine changes to his side handing teenage defender Andreas Christensen a start and bringing in Mohamed Salah, Didier Drogba and Loic Remy.
The Blues looked to be cruising to a comfortable win with Gary Cahill heading home the opener before Ramires grabbed a second shortly before half-time.
Jonathan Stead pulled a goal back before the break and midfielder Filipe Morais, who left Chelsea during Jose Mourinho's first reign at the London club due to a lack of first-team football, equalised 15 minutes from time.
But there was yet more drama when Andy Halliday put Phil Parkinson's side in front in the 82nd minute, and Mark Yeates added a fourth in stoppage time to consign Chelsea to their first home defeat of the season, ending their hopes of winning the quadruple.
