"[West Brom] are a good team and we know they're a good team. With the performance we put out in stages, it may not have looked that way.
"We played OK for the first 10 minutes, then went missing for 20 minutes, then played well for another 10 minutes."
He added: "Half-time probably came at a bad time for us and in the second half and we came out looking like we were going to do something. But unfortunately, Mikel Arteta's sending-off killed us."
Everton's fifth defeat of the season leaves them 16th and just two points above the relegation zone, with an away trip to champions Chelsea to come.
"It's not going to be an easy game away at Chelsea," said Jagielka.
"We'll go there as underdogs and hopefully put a decent performance in and come away with something."
Source: BBC Sport
Source: BBC Sport