"Through my lens, it's hard to look defensive guys in the eyes after a game like this," said Newton, who completed 24 of 50 pass attempts for 324 yards and no touchdowns as the Panthers fell to 0-2 for the first time since 2013. "Offensively, we didn't hold up our end of the bargain.
"All fingers are just pointing back to me specifically on offense."
Newton had 15 off-target throws -- 10 that were overthrown, five underthrown -- the most since Chicago's Mitchell Trubisky in Week 7 last season and the second most in a game for the 2015 NFL MVP's career, according to ESPN Stats & Information research.
In two games, Newton has completed only 61% of his passes to receivers with 3-plus yards of separation, the second-worst percentage in the NFL and down from his 86% last season.
Newton in particular against the Bucs was bad with pressure. He was 0-for-10 when under duress, with three sacks. That was the most such passes he has had in his career without a completion.
"I have to be better," Newton said. "No matter what physical condition I'm in. No matter what, foot, shoulder ... I didn't get the job done, and it's frustrating. I wish I could say something other than that, but that's the fact. I'm a brutally honest person with people, and I'm a brutally honest person with myself. And it's time for me to look myself in the mirror and do some real soul-searching, because I had opportunities tonight and I didn't get it done."
Newton in January underwent shoulder surgery for the second time in three offseasons. He didn't throw most of this offseason, but he wasn't limited in training camp other than planned time off.
Still, Newton's arm strength came under scrutiny after the opener, a 30-27 home loss to the Los Angeles Rams, because Newton had only one pass attempt longer than 20 yards and didn't have a completion longer than 17.
He vowed earlier in the week that the deep ball remained a part of his arsenal, and he seemingly proved it early Thursday night, completing a 44-yard pass to Curtis Samuel that traveled 38 yards in the air.
That was Newton's longest completion by yards in the air since the last game of the 2017 season, according to ESPN Stats & Information data.
But on throws of 15 yards downfield this season, Newton is 4-for-15 (27%) with no touchdowns. He has five interceptions on those balls in his past eight starts, all of which were losses -- six straight defeats before being shut down for the final two games last season and two consecutive losses to open this season.
"We're making something that seems to be simple harder than it is," Newton said. "I don't know what it is. I haven't tasted a win in so long, and I'm not going to make it personal about me.
"It's time for us to accept responsibility, which I am, and move forward."
It's not just his throwing that has been an issue. Newton, who has more rushing yards than any quarterback in the league since he was drafted No. 1 in 2011, hasn't been a threat out of the read-option that he has run most of his career.
In two games, he has five carries for minus-2 yards. He had two carries for no yards against Tampa Bay.
On two fourth-and-1 plays on which Newton used to be close to automatic with the quarterback sneak, he threw an incompletion and was a decoy for running back Christian McCaffrey in the Wildcat formation with the game on the line at the Tampa Bay 2-yard line with 1:21 left.
With Newton not a threat to run, the Bucs stacked the front to stop McCaffrey, who was limited to 53 total yards after having 209 in the opener.
"I don't know," Newton said when asked why his number is not being called in those situations. "I can't answer that question."
Newton didn't blame offensive coordinator Norv Turner for the playcalling, insisting it's up to him to execute whatever is called.
"I say it all the time," Newton said. "Sometimes, you find yourself in a blender, and the only person that can get yourself out is yourself."
Newton takes blame for loss to Bucs
Following Carolina's 20-14 loss to Tampa Bay, Cam Newton puts the blame on himself, saying he's frustrated he "didn't get the job done."