Stoke City coach Mark O'Connor has said he believes the Potters could cause an upset at Chelsea on Sunday.The Blues will be missing skipper John Terry, 29, after the central defender was sent off in the 2-1 defeat by Tottenham Hotspur. [LNB]"I don't think they've got other players of that ability," O'Connor told BBC Radio Stoke. [LNB]"They've got players coming in of a good standard but I'm hoping they'll miss him and that we can exploit that." [LNB]He continued: "By his standards he had quite a poor game against Spurs but he's a top-class player." [LNB]Chelsea are a point ahead of second-placed Manchester United in the Premier League table and Stoke have to play both sides before the end of the season. [LNB]O'Connor said: "We can get something from one of those two games. There's a belief within our squad that we can get something at Chelsea and therefore play a part in what's going to happen." [LNB]The Potters came within two minutes of beating Chelsea at Stamford Bridge in January 2009, having been ahead through a goal from Rory Delap until stoppage time, before going on to lose 2-1. [LNB]Terry scored one of the goals that knocked Stoke out of the FA Cup at the quarter-final stage in March.