Miroslav Klose scored the only goal of the game as the Eagles were beaten by the Coppa Italia winners at Selhurst Park on Saturday.
Holloway believes that the club need a few more bodies before they are ready for the new season.
"We are a bit disappointed with the result but we'll try and get some more players in now," Holloway told the club's official Twitter account.
"I've got to try and find a way that suits this group and without Wilfried we're not quite the same. Probably looking at 4 or 5 more signings. The chairman's worked so hard. He's managed to move hell and high water.
"When you are the favourites to go down, people don't particularly want to come here but I've got to convince them to do that. That group to me looked like we were running on empty today. We need to bring more in. We're a fantastic team and we finished in the top five last season. But we need to bridge the gap to the Premier League."
Palace start the Premier League season against Tottenham Hotspur.