While they finished in the top half last season, fans were unhappy with the quality of football for much of Sam Allardyce's short reign.
"We could not have asked for a better bunch and all the new lads have been great," captain Jagielka told evertontv.
"A few of them are still to get on the pitch but they are trying really hard. The squad is looking very healthy.
"We want to get the new lads out there to make an impact but the boys on the pitch have done a really good job.
"The fact there has not been a desperate need to start six or seven new players has been good. It has been one or two changes at a time.
"Then, if you can slowly build the new players into a team that is confident and playing well, it will be good for them.
"It is a bit different from some previous years when we had four, five or six new players in the side and it was more difficult to settle [as a team]."