(REUTERS) - Everton must stick with under-fire manager Marco Silva if they believe in his ability as there are no guarantees that a new manager can come in and improve results immediately, Manchester City boss Pep Guardiola has said.

Everton invested heavily on new players in the close season but results have hardly matched expectations, with Silva's side managing just three wins in their last 12 English Premier League games to heap pressure on the Portuguese.

"My advice... if they believe in the project, if they believe in him, they have to move forward with him," Guardiola told reporters ahead of Wednesday's (Feb 6) trip to Goodison Park.

"Nobody assures you a new manager is going to do better."

The Spaniard did not enjoy success at City until his second campaign, when he won the league title and the League Cup last season and stressed the need for clubs like Everton to keep faith in their managers.

"It's difficult to create, to build something. You need time, it takes time. So it depends if they trust (Silva) or not," he added.

"The people don't know how difficult it is to create teams. People believe 'I buy three or four players, a new manager, and everything fits perfectly'. Sometimes it takes time."

City are second in the table with 59 points from 25 games, seven places above Everton, who have 33 points.