Chelsea manager Mauricio Pochettino cut a frustrated figure after the Blues' 3-1 loss at West Ham on Sunday, but says it is 'only the beginning' for his side. The Hammers took the lead through Nayef Aguerd after seven minutes at the London Stadium, but Chelsea looked to be on their way to a win as Carney Chukwuemeka levelled later in the half and the Blues won a penalty shortly before the interval. But Enzo Fernandez saw his spot-kick saved by Alphonse Areola and West Ham went back in front through Michail Antonio eight minutes after the restart. Aguerd was later sent off for a second bookable offence, but Chelsea were unable to capitalise and new signing Moises Caicedo endured a nightmare debut as he gave away a penalty in added time and Lucas Paqueta converted to make it 3-1. "It was the frustration when we miss the penalty. We were playing well and we didn't get the reward. We start the second half a little bit with this belief until we started again to play,' he said. "We need to be more strong in this type of situation because we knew West Ham sit deep and counter-attack and set-pieces are really dangerous. "Disappointed but this is only the beginning. We need to believe in the process. I think we are going to be stronger and for sure be really competitive."