The Steelers rookie pass-rusher burst onto the scene with two sacks in his first four defensive plays against the Giants, drawing the attention of older brother J.J. Watt on social media.
Watt nearly had a third sack later in the half, chasing down quarterback Josh Johnson before he got rid of the ball.
"I think just getting out there in general, having a play on (special) teams and then having the sack as I did, it calmed the nerves a little bit," said Watt, who had five tackles, two sacks and three quarterback hits.
"At the same time I felt like I belong here. I came into this game with a certain amount of confidence because of the work I put in."
Coach Mike Tomlin was pleased with Watt's overall play but didn't go too far in his praise during a halftime interview with KDKA-TV (Pittsburgh).
"Those will probably be the two easiest sacks of his [NFL career]," Tomlin said with a smile. "I don't want him to get disillusioned. But I do like the things that I've sent thus far."
On the Giants' first drive, Watt pushed back the tackle and grabbed Johnson as he tried to escape the pocket on third down. The rush from nose tackle Javon Hargrave forced Johnson to run. On the next defensive play, Watt went unblocked and didn't fall for the run fake, resulting in a one-on-one tackle of Johnson.
Watt, the No. 30 overall pick in April's draft, consistently won off the edge, building off his solid training camp. Watt is a candidate to start but might begin the year behind 39-year-old James Harrison.
"I'm trying to get a spot. I don't have time to hit a [rookie] wall," Watt said after a recent practice.
In other Steelers rookie news, wide receiver JuJu Smith-Schuster left the game in the first quarter because of a concussion. The second-round pick finished with two touches for 13 yards. Fourth-round quarterback Josh Dobbs completed 5-of-10 passes for 83 yards and one touchdown, shaking off two early interceptions with a 28-yard touchdown strike to Cobi Hamilton.
Information from The Associated Press was used in this report.