The Bucs entered the game averaging 401.5 yards and 20.5 points per game.
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"I was surprised because I felt like Byron had done a good job and that it was just one of those days where nothing went right," Johnson said. "But had I been the quarterback, I know I would have taken the fall. ... That's the reality of being a quarterback in this league."
Johnson, who was inactive for all 16 games as a rookie, played one fourth-quarter series Sunday and completed 4 of 10 passes for 36 yards while leading a drive that stalled on downs at New York's 5-yard line.
The 23-year-old also finished as Tampa Bay's leading rusher, scrambling for a 15-yard gain on his only attempt.
Morris said he was not blaming the loss on Leftwich, but felt Johnson earned a chance to start Sunday at Washington. The 2008 fifth-round draft pick out of San Diego entered training camp as the fourth-string quarterback.
"I hate to make this about Byron," Morris said, adding that the entire team played poorly against the Giants, who controlled the ball for 43 minutes, 38 seconds while amassing 397 yards total offense, including 226 on the ground against Tampa Bay's porous defense.
"I don't want us as an organization to say that game was all Leftwich ... but Byron is suffering the consequences," the first-year coach said.
Leftwich drops to third on the depth chart behind rookie Josh Freeman, who the Bucs drafted in the first round this year.
The seventh-year pro, a former starter in Jacksonville and Atlanta, won the No. 1 job in an extended battle with Luke McCown during training camp. Following Sunday's game he was asked if thought he would retain the starting role.
"Going into this thing before the season started, I knew we would have to win some games. That's just me understanding and being smart about the whole situation. We haven't done that so far. So no matter whose fault it is or what the reason is for it, we're 0-3," Leftwich said.
"Do I want to remain the starting quarterback of the team? Heck yeah. I feel as though we can still win football games. But we'll see what happens."
Morris decided to make a change after reviewing tape of Sunday's game, citing Johnson's mobility as one of the reasons.
Even though Leftwich was not sacked by the Giants, New York applied constant pressure and the 6-foot-5, 250-pound quarterback has never been much of a threat to run.
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Passer rating: 79.6
Passing yards: 10,218
Passer rating: 50.4
Passing yards: 36
"He provides us more options," Morris said of Johnson, who the Bucs drafted out of San Diego, where he set the NCAA Football Championship Subdivision record for passing efficiency with a 176.68 career rating.
"He gives you the dynamic that you all know about," with his ability to run, the coach added. "He creates a better chance to break out of the pocket and make a play with his feet."
In each of its three losses, Tampa Bay has fallen behind and been forced away from what they do best, which is run the ball.
After gaining 174 yards on 31 carries in the season opener against Dallas, the Bucs had just 19 rushing attempts for 57 yards against Buffalo. They were limited to 28 yards on 10 carries by the Giants.
"We've still got to establish the run," Morris said, stressing that Johnson will need a solid rushing attack to have a real chance to make a difference. "That's where it's got to start."
The new starter said he's ready for the opportunity.
"It's not just about me turning this thing around," Johnson said. "It's about all of us turning this thing around to start getting some wins."
Copyright 2009 by The Associated Press