Sir Alex Ferguson has been discussing his team's chances ahead of their West Ham clash this weekend. The Hammers have been improving under boss Gianfranco Zola and Sir Alex knows it could be a tough game. United have not lost a Premier League game since they played Arsenal in November, which was also the last time the Red Devils conceded a league goal. This record-breaking run has taken Sir Alex's side to the summit of the table, where they sit two points above Liverpool with a game in hand. But, West Ham are currently six games unbeaten and will be hopeful of upsetting the champions after holding Arsenal to a draw on January 31. And Sir Alex has injuries to contend with, as striker Wayne Rooney and full-back Patrice Evra are still not back to full fitness. The manager said of Sunday's clash: "Wayne Rooney and Evra, Patrice Evra, won't start the game. But it's very possible they could be on the bench. They're not 100 per cent, but they're coming on." He continued: "We've a difficult game on Sunday. It's always difficult going to West Ham. We've lost two titles there, so we know the extent of the challenge. "And also, it's a team that, through Zola in the last few months, has improved a lot. And given the fact he's had to sell players, he's done a remarkable job in getting to the level they're playing at at the moment."