Having played under David Moyes for six years, Mikel Arteta knows just how good he is.
The Scot's West Ham side are the surprise package of this season, and head into Sunday's game at the London Stadium in fifth place in the Premier League.
When asked whether he was surprised by the Hammers' form this term, Arteta was emphatic in his response.
"Not really," he said. "I think they have a really strong squad and they have a great manager and coaching staff.
"They started the season with some doubts but I know what David is capable of doing. He gets the group together, they're working really hard for each other, they've recruited really well and you can start to see the things that David has done.
"Obviously they have a little bit more time during the week to prepare football matches and training, and I think they've been in great form and they're a really dangerous team."
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