In what otherwise was a self-serving gripe, Larry Johnson inadvertently made a point two weeks ago about coaching. He claimed the same plays kids draw up in the dirt become rocket science to NFL coaches who work 18 hours a day for seven-figure salaries.

“Football is easy,” Johnson said. “It’s not a chess game. It’s checkers. When they’re looking for the run, you pass. When they’re looking for the pass, you run. When they put nine in the box, you pass. When they overload one side, you run to the other side.”

Johnson’s point was graphically demonstrated last week by several losing coaches.

¢ Houston’s brain trust, led by former NFL quarterback Gary Kubiak, pitched out to Ron Dayne (Ron Dayne?) on third-and inches-at the goal line in last week’s loss in Atlanta.

¢ Andy Reid and Marty Mornhinweg, the coach and offensive coordinator of the Philadelphia Eagles, left Winston Justice, a second-year tackle making his first NFL start, on his own against the Giants’ Osi Umenyiora. Later, they suggested that “only” four of Umenyiora’s six sacks were Justice’s fault.

¢ Norv Turner, one of the NFL’s best offensive minds, gave the ball to LaDainian Tomlinson only six times in the second half of San Diego’s 30-16 loss to Kansas City last week after the NFL’s 2006 MVP ran for 116 yards in the first half and the Chargers led 16-6.

¢ Minnesota’s Brad Childress did the same with rookie standout Adrian Peterson, who carried 12 times for 112 yards in the first half against Green Bay, then got the ball only twice after intermission.

How about some more specifics on last week’s coaching foibles, starting with two games that pitted teams against coaches who worked for them as recently as a year ago and now work for their opponent?

Cardinals coach Ken Whisenhunt and top assistant Russ Grimm both were longtime Pittsburgh assistants and both were finalists for the job that went to Mike Tomlin.

So the Steelers, who were averaging almost 200 yards rushing per game, were held to 77 yards, 26 on scrambles by Ben Roethlisberger, last Sunday at Arizona. Willie Parker had 19 carries for 37 yards; take away one 20-yard run and he averaged less than a yard a carry.

“I think coach Whis knew some of the weak points of our offense,” Pittsburgh wide receiver Santonio Holmes said. “He was sending guys left and right, bringing pressure as much as he could to try to disrupt our offense. They did a pretty good job of it.”

Add in the grudge factor and … Arizona 21, Pittsburgh 14.

In the night game at the Meadowlands, some more inside information was helpful.

Steve Spagnuolo, the Giants’ defensive coordinator, was the linebackers’ coach of the Eagles from 1999-2006 and was hired specifically to bring the aggressive schemes used by Jim Johnson up the New Jersey Turnpike. It didn’t work for two games in which New York surrendered 80 points.

But it sure worked against the Eagles, who should have been prepared.

Still, it begs the question why Justice, a second-round pick last year who was inactive for all 16 games as a rookie, wasn’t given a tight end or fullback to block Umenyiora. When in form, Umenyiora is one of the NFL’s most dangerous pass rushers.

The “help” instead went to Jon Runyan against 35-year-old Michael Strahan, a strange choice given Runyan’s experience combined with Strahan’s age and rust after holding out for almost all of the preseason.

Even Strahan, who had one of the Giants’ 12 sacks, saw the problem.

“That poor kid that they had over there,” Strahan said of Justice, filling in for the injured William Thomas. “Why didn’t they help him? I felt, in an odd way, you could ruin the guy. It’s his first start and that’s what he gets. It’s not a good thing.”

Reid later conceded, “I could’ve done a better job there, with that part, giving him help.”

New York 16, Philadelphia 3.

Out in San Diego, after averaging 2.3 yards per carry in three games, Tomlinson finally broke out in the first half against the Chiefs, a team with about half the talent of the Chargers. In the second half, he disappeared as Kansas City outscored the Chargers 24-0.

That’s because Turner depended on Philip Rivers, who hasn’t been very dependable this season. He finished 21-of-42 for 211 yards with two interceptions and a fumble that led to 17 points. His passer rating was 44.8.