When asked if it was their worst display in the competition, the 52-year-old Israeli coach, who left Frank Lampard and John Terry out of his starting line-up, replied: "Yes, it was a game in which we played less well.
"The result is okay, although you always want to win. A draw away is not a bad result but we didn't create a lot of chances and that was disappointing.
"It is not easy to play against Olympiacos. They are a very organised team. We will try to improve for the return leg."
Grant refused to confirm whether Lampard or Terry will start the Carling Cup final against Tottenham at Wembley on Sunday.
He said: "I need to tell the players first and not the media."