LONDON - Arsenal forward Theo Walcott has warned resurgent arch-rivals Tottenham Hotspur they are travelling across North London for their eagerly-anticipated FA Cup third round tie at a bad time.The two sides meet on Saturday at the Emirates with Spurs in a rich vein of form having collected 10 points from a possible 12 in the English Premier League since Tim Sherwood replaced Andre Villas Boas as manager last month.But Walcott has scored five goals in his last five games as Arsenal returned to the top of the table after a brief slip at Christmas and the England international went on the offensive when asked if it was bad time to play Sherwood’s in-form Spurs."It’s going to be a bad time to play us as well,” he said in quotes carried by British media on Friday. "For the neutrals, it’s going to be a very interesting battle. I can’t call it. It’s one of those games that’s going to be very open. The FA Cup is always special for me, being English. I love the FA Cup. "Since their new appointment, Tottenham have done very well, to be fair to them. But like I say, they won’t want to play us. And it’s at The Emirates. We’re trying to make our stadium into a fortress and we are starting to do that.Walcott started the last time the two sides met, a 1-0 league victory for Arsenal in September where Villas Boas’ side pushed hard for an equaliser in the second half but could not find a way through. Goals, though, have not been a problem for Spurs under Sherwood, with nine coming in league wins over Manchester United, Southampton and Stoke City. Arsenal had attacking trouble against Cardiff City on Wednesday with the Welsh side proving resolute before substitute Nicklas Bendtner lashed home a late goal at the Emirates and Walcott combined neatly with England colleague Jack Wilshere in the dying stages to complete a 2-0 league success. It was a win the 24-year-old Walcott said proved his side had the stomach for a title fight as they bid to win their first trophy since defeating Manchester United on penalties to lift the FA Cup in 2005. "Wins like Cardiff prove we are serious contenders,” Walcott said.Both side’s have key injury concerns for Saturday’s clash with Mesut Ozil, midfielder Aaron Ramsey, Bendtner and fullback Kieran Gibbs all likely to be out for Arsenal.Sherwood said after Tottenham’s 2-1 win at Old Trafford on Wednesday his squad were down to the bare bones with former Arsenal striker Emmanuel Adebayor - who has scored three times in four games since being recalled - the latest doubt after being carried away on a stretcher against United.