Harrell completed 13 of 15 passes for 223 yards with two touchdowns in both teams' final preseason tuneup.
"It was just doing what we've done all year, just more consistently," Harrell said. "When things are going well, I think all of the guys start to feel it - you get some momentum, you get more emotion - and I thought the tempo was up just a little bit. When things are going well, you kind of start rolling."
"We talk about it all the time: It's nice when people say nice things about you and it's not so nice when they don't," McCarthy said. "And it's one extreme to the other, particularly at that position. That's part of the deal. I think he handled it very well."
But with the final round of roster decisions looming Friday, McCarthy stopped short of making a definitive declaration when asked if he was comfortable going into the season with Harrell as the backup.
"I think he definitely grew through the preseason, topped it off with an excellent performance tonight," McCarthy said. "But we're not going to make any roster selections here tonight."
Peyton Hillis had 46 yards on six carries, and said the offensive line showed improvement from last week.
"It was a great job up front," Hillis said. "That's where we found the holes. I think as far as coming out and trying to work the running game and try to get that accomplished, I believe we did that."
Defensive tackle B.J. Raji appeared to hurt his left ankle on the Packers' first defensive play, but was able to walk off the field without assistance. Raji did not return to the game, but McCarthy said he wasn't particularly concerned about the injury.
The two teams had a combined total of 22 penalties, but it seemed an indication of sloppy play rather than mistakes by the replacement officiating crew.
Chiefs starting quarterback Matt Cassel came out of the game a few plays into their second possession. Brady Quinn was 6 of 12 for 83 yards with an interception, while Ricky Stanzi and Alex Tanney struggled to move the ball.
Crennel said Quinn was "decent," with room for improvement.
"He's my second quarterback, so I'm going to ask him to step up like I would ask anyone else to step up," Crennel said.
After Rodgers played the first two series, Harrell took over early in the second quarter.
He seemed to gain confidence after Jermichael Finley made an acrobatic catch for a 27-yard gain. Harrell found Tori Gurley wide open for a 54-yard gain on the next play and Green ran in for a 2-yard touchdown two plays later for a 7-3 lead.
Harrell and the Packers got the ball back at their 7-yard line on the next series and Harrell drove them downfield, eventually throwing a pass to Green for a 17-yard touchdown.
After halftime, Harrell put together another steady drive, eventually finding Boykin again for a 12-yard touchdown.
Coming into Thursday, Harrell had completed 50.8 percent of his passes with a touchdown and two interceptions. However, Harrell has been playing with a second-string offense that has struggled to give him any help, especially in pass protection. He was sacked five times in the first three games.
Now he hopes he has sealed his spot on the roster.
"I want to play as long as they let me," Harrell said. "It was fun tonight, and I love the game. I get to play a game as a professional right now. As long as they let me do that, I'll do it."
Notes: DB Charles Woodson, C Jeff Saturday and WR Donald Driver were among the players who did not dress for the Packers. ... Kansas City's Patrick DiMarco blocked a punt in the third quarter, but Packers rookie S Jerron McMillian picked it up and ran for a first down. ... Succop missed a 54-yard field goal.
Copyright 2012 by The Associated Press