Michael Paranay, Dquay Means and Jerrell Whitlock are facing charges ranging from conspiracy to attempted homicide. Lawyers for the three men claim Adams lied about the details of the incident.
Opening statements took place on Tuesday.
Adams, an offensive lineman, was hospitalized for four days after the June 2013 incident.
The alleged stabbing and carjacking took place at about 3 a.m. in the city's South Side.
The Steelers drafted the 6-foot-7, 325-pound Adams in the second round in 2012 out of Ohio State.