The defender, a free agent after leaving Sunderland, played in Town's 2-1 friendly win over Gillingham on Tuesday night.
McCarthy, who also handed trials to Frederic Veseli and Bongani Khumalo, admits he is interested in bringing the 31-year-old back to Portman Road 11 years after he left to join Newcastle for £6million.
"Bongani and Freddy did really well and Titus did what Titus had to do," McCarthy told the club's official website.
"I only met up with Titus for the first time at our pre-match meal. He asked if he could come in for training and wanted to play.
"He's obviously interested in coming here and we are interested in him otherwise he wouldn't be playing for us. He showed a good commitment to come and play but it's early days yet. No more than that."