The third-round pick completed 10 of 13 passes for 154 yards and impressed McCarthy with his poise and decision-making.
Will Howard also caught the eye, completing seven of nine passes for 86 yards and directing a touchdown drive as the Steelers outgained Green Bay 385-160.
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Mason Rudolph was similarly efficient in his brief outing, heightening competition for the backup quarterback spots behind Aaron Rodgers.
Jordan Love made a short appearance for the Packers, while rookie kicker Trey Smack was a bright spot, converting field goals from 58, 38 and 37 yards.
Cardinals 27-14 Raiders
No 1 overall pick Fernando Mendoza threw a touchdown pass in his preseason debut but the Las Vegas Raiders fell 27-14 to the Arizona Cardinals.
Mendoza completed 10 of 16 passes for 97 yards and found rookie receiver Jack Bech for a six-yard score, becoming the first top draft selection since Baker Mayfield in 2018 to throw a touchdown in his first preseason appearance.
Veteran quarterback Kirk Cousins also threw a touchdown in a sharp one-series cameo for Las Vegas.
Arizona built its advantage behind flawless passing from Jacoby Brissett and former Raider Gardner Minshew, while third overall pick Jeremiyah Love impressed with 58 rushing yards on 11 carries.
Colts 13-13 Patriots
Anthony Richardson returned from injury with a mixed display as the Indianapolis Colts drew 13-13 with the New England Patriots in their preseason opener.
The former first-round pick threw for 145 yards and scored on a one-yard quarterback sneak, but also lost a fumble and had a pass intercepted as Indianapolis committed four turnovers.
Tommy DeVito led New England's offence, completing 13 of 22 passes for 128 yards and a touchdown to Kyle Williams.
The Colts rescued the tie with a 61-yard field goal from Spencer Shrader late on, while Anthony Borregales missed a potential game-winner for the Patriots.
Titans 19-13 49ers
No 1 overall pick Cam Ward endured a mixed preseason debut as the Tennessee Titans beat the San Francisco 49ers 19-13 in their exhibition opener.
Ward led a 95-yard touchdown drive on Tennessee's opening possession but finished with just 25 passing yards, completing five of 10 attempts while failing to connect with fellow rookie Carnell Tate.
Tony Pollard scored the Titans' only touchdown and Joey Slye kicked four field goals, including three from beyond 50 yards.
San Francisco backup Kurtis Rourke impressed on his return from injury, completing 12 of 14 passes for 101 yards before leaving with a rib injury, while rookie receiver De'Zhaun Stribling caught seven passes for 63 yards.
Chargers 27-7 Texans
Amar Johnson scored twice and produced a spectacular 55-yard reception as the Los Angeles Chargers opened their preseason campaign with a 27-7 victory over the Houston Texans.
The undrafted running back, entering his second season, rushed for two touchdowns and added a two-point conversion as the Chargers pulled away in the second half.
With starters Justin Herbert and C.J. Stroud rested, Trey Lance completed 12 of 20 passes for 164 yards for Los Angeles, while Davis Mills threw Houston's only touchdown pass.
DJ Uiagalelei also impressed, throwing a late touchdown, as the Chargers dominated after the break in Houston.
Lions 14-16 Bengals
Joe Flacco threw a touchdown pass in relief of Joe Burrow as the Cincinnati Bengals opened their preseason with a 16-14 victory over the Detroit Lions.
Burrow completed five of six passes for 39 yards in two early series before giving way to Flacco, who found rookie tight end Jack Endries for a score.
Evan McPherson added three field goals, including a 56-yarder, while the Bengals capitalised on three Detroit turnovers.
Undrafted rookie Luke Altmyer threw for 130 yards and a late touchdown for the Lions, who threatened a comeback before Russ Yeast sealed the result with a late interception.
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