Sam Allardyce's side have not won in their last four Premier League outings, with their most recent defeat coming against Norwich City on Saturday.
Despite the 3-1 loss at Carrow Road, which saw West Ham surrender the lead handed to them by Ravel Morrison, Nolan is confident things will get better.
"We've just got to keep plugging away because one day it will turn for us and that's what we've got to keep believing," he told the club's official website.
"We have got a great squad here and a group of lads well capable of being in this league, so we've got to work towards being where we believe we should be - in the middle of the table.
"We're not there at the moment, so we've got to face facts and get on with it and make sure we're ready for Chelsea and, believe me, we will be."
West Ham take on London rivals Chelsea and Fulham at Upton Park in their next two fixtures as they seek to climb from 16th in the table.
Nolan claims positive results from those two fixtures could mark a turning point in the club's season.
"If we can take points from those games then we'll start looking upwards," he said.
"We're under no illusions that we're not where we want to be and it's been a tough old season so far.
"But we've got a long way to go and we're determined to put it right and I'm sure we will."
