"I know what to expect now," he said Thursday. "I'm not stepping out there for the first time -- not going out there wide-eyed anymore."
The Browns named Thompson-Robinson their starter for Sunday's game against the Pittsburgh Steelers after Deshaun Watson was lost for the season with a fracture in his throwing shoulder. Watson injured the shoulder during this past Sunday's 33-31 win over the Baltimore Ravens.
Thompson-Robinson started the first meeting against the Ravens on Oct. 1 in Week 4 while Watson was dealing with a different shoulder injury, a rotator cuff strain. Thompson-Robinson, however, didn't know he was starting until Watson's pregame warmup determined he couldn't play just a couple of hours before kickoff.
Thompson-Robinson threw three interceptions and took four sacks, as the Ravens won 28-3.
Thompson-Robinson said he learned a lot from that experience and noted he feels better prepared for the Steelers.
"I know what it takes now to be an NFL quarterback, not just a college quarterback," he said. "I think I've taken that next step."
The Browns drafted Thompson-Robinson with a fifth-round pick out of UCLA, where he was a five-year starter. He impressed during the preseason and earned the No. 2 job behind Watson after the Browns traded quarterback Joshua Dobbs to the Arizona Cardinals.
But after the loss to the Ravens, the Browns elevated PJ Walker to the starting role while Watson recovered. Walker won two straight games as Cleveland's primary quarterback but threw a critical interception late in a loss to the Seattle Seahawks on Oct. 29.
After Watson's season-ending injury, the Browns decided to give Thompson-Robinson another shot.
"That was a tough spot that he was in," Browns coach Kevin Stefanski said of Thompson-Robinson's first start against the Ravens. "I think this week, having a full week of preparation, knowing that he's going to be the starter, I think is important."
The Browns face the Steelers in another key AFC North matchup. Both teams are 6-3 and a half-game behind the first-place Ravens (7-3) in the division.
"You have to win," Thompson-Robinson said. "It's a must-win game. Not only just for this week but for our future, what we're trying to get to and the goals we're trying to get to. So it's a big game. At the end of the day, if I go out there and follow my rules, I'll be all right."