Chelsea were booed off at the end of the game and Grant removed misfiring striker Shevchenko early in the second half for the second successive league game.
The Israeli coach conceded the former AC Milan star was still not at his best but remained positive as his side prepare for their trip to Spain in the Champions League.
Grant said: "Shevchenko is a very good player but today he was not at his best. He is a good player still.
"We have only played eight games in the league and to judge players we have to wait until after 20 or 25 games and then we can say whether he was good or not.
"First we need to score and then we need to win. I can't argue with that. We need to play better and I think the players want to do that. We need to improve a few things in the game.
"We were not at our best today but I believe in the players and that we can go forward. Most of the fans are behind us."