Premier League strugglers Swansea were humbled in a 3-2 loss at fourth-tier Oxford on Sunday for the first big shock in the third round of the FA Cup.
Chelsea endured third-round humiliation at the hands of lower-league opposition in Bradford last season but had no problems 12 months on, beating Scunthorpe 2-0 through goals by Diego Costa and Ruben Loftus-Cheek.
Fifty-four places separated Swansea and Oxford in the English football pyramid and Ecuador winger Jefferson Montero gave an indication of the supposed difference in class by backheeling the visitors into the lead in the 23rd minute.
However, Oxford scored three goals in 14 minutes either side of the halftime break and Bafetimbi Gomis' 66th-minute reply proved only a consolation for Swansea.
Swansea, which is in the midst of a relegation fight in the Premier League, came unstuck after making 10 changes for the game.
"All credit to Oxford, they were more energetic than us and passed the ball better," Swansea manager Alan Curtis said. "We made changes but we still had lots of experience, but Oxford thoroughly deserved to beat us."
Four Premier League teams were eliminated on Saturday, but only after losing to fellow top-flight sides.
Chelsea remained unbeaten under Guus Hiddink, who took over until the end of the season after Jose Mourinho's firing last month, but it wasn't a convincing performance by the seven-time FA Cup winners.
Under pressure from two defenders, Costa turned in Branislav Ivanovic's right-wing cross for the 13th-minute opener. Loftus-Cheek, a halftime substitute, ended Scunthorpe's resistance in the 68th.
Hiddink guided Chelsea to the FA Cup title in 2009, also as an interim manager.