BALTIMORE -- The winless Buffalo Bills sent home defensive tackle Marcell Dareus, lost quarterback Tyrod Taylor to injury and made far too many mistakes against the Baltimore Ravens, who remained undefeated in the preseason with a 13-9 victory Saturday night.

Though starting quarterback Joe Flacco has yet to take a snap at camp this summer, the Ravens (3-0) have relied heavily on their retooled defense to win.

Baltimore has allowed only two touchdowns in three games -- none by the starting unit -- and now stands one victory short of completing a second straight unbeaten preseason.

"I love the way our guys are playing," coach John Harbaugh said. "Not one negative vibe."

Buffalo (0-3) is still looking for its first win under rookie coach Sean McDermott, who's got far more important issues to address, such as the behavior of Dareus and the health of Taylor.

Dareus was exiled by the Bills before the kickoff for violating a team rule. Buffalo general manager Brandon Beane called the transgression "disappointing" and did not rule out the possibility of further discipline beyond the one-game suspension.

McDermott said: "I'm disappointed. We're disappointed. My hope is he'll learn from this and we'll move forward."

Taylor sustained a concussion at the end of Buffalo's second possession when sacked by Matthew Judon. After being assessed on the sideline, Taylor was removed from the game after going 1 for 3 for 1 yard.

"He's in the protocol at this point. Nothing further at this time," McDermott said.

Backup Nate Peterman went 11 for 23 for 93 yards. Third-stringer T.J. Yates entered in the third quarter and had his first pass intercepted -- a turnover that Baltimore converted into a touchdown for a 10-7 lead.

Buffalo was penalized nine times for 64 yards. Several of the flags came at the worst time, wiping out first downs and solid kick returns.

Finally, with 1:04 left, rookie receiver Brandon Reilly lost a fumble at the Baltimore 8 to end the Bills' final chance to win.

"You can't do that," McDermott said. "Fundamental football, taking care of the football, we didn't do a good job of that at the end."

TEMPORARY STARTER

Ryan Mallett, who's been starting in place of Flacco for Baltimore, went 6 for 10 for 58 yards in less than a half.

Harbaugh bristled when asked to reveal a timetable for Flacco's return. The Ravens have said Flacco will start the season opener against Cincinnati, but it's still uncertain when he will join his teammates on the practice field.

"He will be back for the Bengals game, I promise you that," the coach said. "Do you really care when he's going to practice?"

CLOSE CALL

Ravens kicker Justin Tucker had to undergo concussion protocol after being hit in the neck while trying to make a tackle on a second-quarter kickoff. "It was about trying to make a play," said Tucker, who was cleared to return but stayed on the sideline. Kenny Allen kicked an extra point and a 40-yard field goal in the second half.

ROOKIE WATCH

Bills: WR Zay Jones, a second-round selection, was targeted eight times and had three catches for 28 yards.

Ravens: Undrafted free agent RB Taquan Mizzell, out of Virginia, made an impression with six catches for 54 yards and a touchdown. He also had six carries for 14 yards.

POSITION BATTLES

Bills: Fifth-round pick Peterman was the first quarterback summoned after Taylor went down and appears to have locked down the backup role after starting camp behind Yates.

Ravens: Signed as a free agent earlier in the week, C Jeremy Zuttah returned to his familiar spot in the middle of the Baltimore offensive line and could press Ryan Jensen for a starting spot.

RAISED FIST

While many of his teammates put their hands on their hearts during the national anthem, Bills tackle Cameron Jefferson raised his right fist. Jefferson has done so previously, saying he's protesting racial inequality.

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