Lukaku struck twice in victory over the Seattle Sounders this week.
"It's interesting to see him playing with the team," Di Matteo said. "We've had a talk at the start of pre-season and I'm very keen to see him perform for us, then we will see what's going to happen. He is a danger and scores goals. That's what a striker has to do in the team.
"We still have Fernando and Sturridge to come back but we have options and we can't forget he is a young boy but I have been pleased and he is an interesting player for us."