Don't worry if big, powerful Derrick Johnson sees you stealing his parking space.
He'll probably just give you a "tsk-tsk" look and drive away.
If he sees you in an opposing uniform carrying a football, do worry. That's when Mr. Nice Guy becomes Mr. Nasty.
It's almost as though Kansas City's sixth-year linebacker, who is playing the best football of his life, has multiple personalities. Away from the game, he's a milquetoast, someone who's darn near impossible to upset.
"Derrick is nice and quiet off the field, a great guy," coach Todd Haley said.
But stick him in a football game and smiles turn to snarls as he channels his inner Dick Butkus.
"He cranks it up on Sunday," said Haley with a grin, adding, "I'm glad he does."
Haley and the Chiefs were never happier with their quick-hitting inside linebacker than last Sunday in Oakland when he played what may have been the best game of his career.
Not only did Johnson have 12 solo tackles, he also got credit for three of four stops in the key defensive series of the game, a second-quarter goalline stand while KC was protecting a 14-0 lead.
The secondary stole the show with six interceptions and cornerback Brandon Flowers was selected the AFC defensive player of the week. But Flowers insists he ought to share honors with Johnson.
"Man, he's having a stellar, stellar year, the best I've ever seen him play," Flowers said. "I said I have to share player of the week with him. He does all the dirty work. All the defensive backs and quarterbacks get all the glory, but Derrick Johnson has won a lot of games for us."
And off the field?
"Nicest guy you'll ever meet," Flowers said.
It's true, says Johnson. His Jekyll-and-Hyde personality even amazes himself.
"I'm so much of a humble guy off the field," he said. "That's just how I grew up. Everybody sees me as a real chilled guy. On the field, there's a switch that goes on. I get quick-tempered."
It's not that he makes an effort.
"It's natural," he said. "And I like that it's natural. Sometimes when you get into that (motivation) thing — 'Man, I've got to do something to make myself get up,' that's not going to happen. I'm such a nice guy off the field, it's amazing how I can get on the field and have a quick temper. A crazy temper."
So off the field, he never gets mad at anything?
"I can't say that. But I have a control of myself off the field."
When Haley took over as head coach in 2009, Johnson was known as an underachiever, a first-round draft pick who'd never lived up to the billing that came with his winning the Butkus Award as the nation's best college linebacker.
The first year under Haley was the most miserable of his career. He hardly ever started.
But during training camp in 2010, he said he was a better player than he'd been, and went out and finally established himself as NFL linebacker to be reckoned with. He led the AFC West champs with 147 tackles. He had one game where he intercepted two passes and returned them for touchdowns.
But not even that eclipsed what he did Sunday in Oakland when the Chiefs, after an 0-3 start, evened their record at 3-3 and set up a Monday night showdown with San Diego that'll have first place in the AFC West on the line.
"Derrick's game was as good as I've seen him," Haley said. "A couple of plays he made were truly just monster plays in the game as far as keeping it, going the direction we wanted it to go. He was right in the middle of it so many times."
In practice, even Johnson's teammates were impressed with how he was doing.
"I heard players talking during practice last week. Derrick hit somebody on one of the days we were in pads and somebody said, 'He's a striker.' He can be cruising along and, 'Bam!' He has that ability to leverage and knock people around. some of those plays (against Oakland) were just phenomenal."
As long as he has football as an outlet, Derrick Johnson is not likely to get mad at anything.
"I like football because on the field, that temper can go off and it's great," he said.