West Ham manager Slaven Bilic was left frustrated after his side missed the chance to keep pace with the Premier League's top four by losing 2-1 at Newcastle United on Saturday.
Bilic's men lost for the first time since November after early goals by Ayoze Perez and Georginio Wijnaldum put Newcastle in charge.
Nikica Jelavic gave West Ham hope by scoring two minutes after his half-time introduction as a substitute, but the closest West Ham came to an equaliser was a late Cheikhou Kouyate header.
Bilic told Sky Sports: "We are frustrated of course, because we were on a good run and we were unbeaten, playing good, picking up points, fifth in the table, so we wanted to continue that and get something out of this game - a point or three points.
"For me, it is much more frustrating how we started the game and how we played in the first half.
"It was way below par and we just couldn't match the sharpness, the quickness, the aggression in the middle of the park.
"For a lot of situations in the first half we were simply not good enough."
Bilic added that West Ham "improved a lot" in the second half after working on their shape.
"We were aggressive, we created a few chances and at the end we had a great chance to make it 2-2," he said.
"But to be fair they deserved to beat us today."
Bilic added that he is unlikely to bring in new players during the January transfer window.
"Every team can improve but we made a plan that we will be very active in the transfer window when summer comes," he said.