Defenders Branislav Ivanovic, Ashley Cole and David Luiz and midfielders Ramires and Raul Meireles are all one booking away from an automatic one-game ban ahead of the London club's bid to avenge their defeat at the same stage three years ago.
Only four of those are likely to play as Luiz is out injured but Di Matteo said all the players would be concentrating on executing a game plan that will see them through to next month's final in Munich.
"I don't think we can be thinking about that in the game tomorrow," the Italian, who has revived Chelsea's fortunes since taking over on a temporary basis last month, told a news conference at Barca's Nou Camp stadium on Monday.
"The players are going to be fully focused on their tasks and whatever happens, happens," he added. "We can't be distracted by the bookings."
Di Matteo declined to reveal whether Didier Drogba, who scored Chelsea's goal in the first leg at Stamford Bridge, was likely to have shaken off a knee injury in time to feature.
"We have the final training session after the press conference where I will assess the physical and mental state of all my players," he said.
"Then I will make the team selection tomorrow morning so I can't tell you exactly what it is. Tomorrow night."
CECH IRONY
Both Di Matteo and goalkeeper Petr Cech were asked the inevitable questions about former Chelsea manager Jose Mourinho, whose Real Madrid side beat Barca 2-1 at the Nou Camp on Saturday to close in on a first La Liga title in four years.
Cech sought to lighten the mood with an ironic answer to a query about whether they had sought the Portuguese's advice.
"Yeah we had a tactical meeting a few hours ago," Cech said with a straight face, prompting laughter around the media room. "He sent over the whole file and we tried to get it all down."
Cech said he did not think Barca's defeat by Real, which left them seven points behind their arch-rivals with four games left, would have a big impact on their performance on Tuesday.
Barca are making a fifth consecutive appearance in the last four as they bid to become the first team since AC Milan in 1990 to win consecutive European Cups.
Chelsea are chasing their first continental title and are through to the semi-finals for the sixth time in nine years.
"They are an experienced team and they know how to handle defeats," Cech said.
"I think the game tomorrow will be similar to the first leg," he added. "We hope to score a goal and that will have a big impact on the match."
