Mularkey made the announcement after he watched the veteran backup provide poise and focus to the offense, leading the Bills to a 27-17 win over the New York Jets on Sunday.
"If it'll put everybody at ease, I'm going to start Kelly next week against the Raiders," Mularkey said.
That's a switch after Mularkey refused to reveal his starter the last two weeks.
But Holcomb is proving to be the obvious choice after he won his second straight start in place of J.P. Losman, the 2004 first-round draft pick who struggled in starting the first four games this season.
Shrugging off two interceptions, Holcomb went 18-of-26 for 172 yards and two touchdowns in helping the Bills produce a season-high 27 points.
Buffalo (3-3), in a tie with New England atop the AFC East standings, is suddenly looking nothing like the sloppy team that combined for 26 points in three straight losses before Holcomb took over.
"The bottom line is we won the ballgames," Holcomb said. "It doesn't matter about statistics or anything. ... We've won the last two. We've got ourselves back to .500."
By providing the Bills with an efficient passing attack, Holcomb opened running lanes for Willis McGahee. The third-year running back finished with a career-high 143 yards rushing and a touchdown.
"Pick your poison," Holcomb said. "We have guys that can make plays. And I try to get them all involved."
The Jets (2-4) have lost five straight road games dating to last season.
Curtis Martin led New York with a season-high 148 yards rushing and caught two passes for 3 yards, becoming the seventh player to gain 17,000 yards from scrimmage with a 41-yard run in the third quarter.
Martin, who was averaging 57 yards rushing a game, also had a 49-yard gain, his longest since Dec. 14, 2003.
Vinny Testaverde was inconsistent making his second start since the quarterback-depleted Jets signed the 19-year veteran last month. He finished 12-of-26 for 161 yards and two interceptions, and scored on a 1-yard plunge.
"I guess the honeymoon's over," Testaverde said. "I certainly didn't come back to lose, and I'm going to try and do everything in my power to get better."
It wasn't all Testaverde's fault. The Jets had difficulty containing a Bills offense that finished with a season-high 341 yards.
"We couldn't find a way to eliminate the running game," linebacker Jonathan Vilma said.
Holcomb was at his best by shrugging off his mistakes.
The Jets got back in the game when linebacker Mark Brown intercepted a pass and returned it 18 yards to the Buffalo 2. Testaverde scored two plays later to cut Buffalo's lead to 24-17 late in the third quarter.
Holcomb responded, marching Buffalo 56 yards on 10 plays -- eating up nearly 6 minutes of the clock -- to set up Lindell's 38-yard field goal with 6 minutes remaining. The best play was Holcomb hitting tight end Mark Campbell for a 24-yard reception to convert second-and-14.
The defense then did the rest, forcing two turnovers on the Jets' final three possessions. The decisive one was Terrence McGee's interception at the goal line with 3 minutes remaining.
Buffalo finished with three turnovers and five sacks while limiting New York to 275 yards of offense.
Bills players are backing Holcomb.
"Kelly did a great job," McGahee said. "He's a vet. He knows what's going to happen. He knows he can rebound from it. Just keep your confidence, and that's what he did."
Holcomb was equally impressed with McGahee.
"It's refreshing knowing that when you hand the ball off to this guy, he can make plays," Holcomb said. "I just sit back there and marvel sometimes at what he does."
- McGahee scored in the third quarter, the Bills first second-half touchdown of the season.
- Jets C Kevin Mawae didn't return after hurting his elbow in the second half. Coach Herman Edwards would only say that Mawae will have tests to determine the extent of the injury.
- Jets PK Mike Nugent hit a 44-yard field goal.