Denver ? Just like many of the players they lead, successful NFL coaches have a most unfortunate flaw: They rarely know when it’s time to go.

In his 10th season with the Denver Broncos, it’s looking more and more like that time has come for Mike Shanahan. But unless the owner, Pat Bowlen, changes his mind, it’s not going to happen.

“He’s got four years to go on his contract, and I’m not firing him,” Bowlen said recently, standing firm on a stance he took many months ago.

Bowlen is loyal to Shanahan largely because of the two Super Bowl titles the coach brought to Denver, a city that long yearned for a championship.

The more recent history isn’t as flattering, though. Since Denver’s last Super Bowl victory six seasons ago, 20 of the NFL’s 32 teams have won playoff games, and Denver is not one of them.

In total command of the coaching and personnel fronts, Shanahan put together a record during the past six seasons that would cost many coaches without Super Bowl rings their jobs.

Since they won the Super Bowl and John Elway retired, the Broncos are 52-42, 0-2 in the playoffs. They start fast — 13-3 over the first quarter of the last four seasons — and finish poorly — 22-24 over the final three quarters of those years, with two games still to go in 2004.

Their 45-17 loss to Kansas City on Sunday, for which Shanahan took the blame, dropped Denver to 8-6 and left the Broncos in jeopardy of missing the playoffs.

Not that it would matter much. A trip to Indianapolis for a first-round playoff game might be worse than just ending the season Jan. 2 at home against Peyton Manning and the Colts in the regular-season finale.

Shanahan’s faults have been debated rigorously around Denver during the past few weeks.

Conclusions: As a coach, he is known as “The Mastermind,” but without the talent to put his game plans into action, he looks like a C student.

Denver coach Mike Shanahan watches from the sidelines as his team loses to the Chargers. The game was Dec. 5 in San Diego.

The quick starts and staggering finishes each season reveal a coach who comes out with great schemes, then does little to counter the adjustments opposing coaches make.

As a personnel man, Shanahan picked up Terrell Davis in the sixth round, turned Shannon Sharpe into a star and brought out the brilliance in Rod Smith.

But the more recent record has been spotty at best.

The decision to trade for Champ Bailey might have been the right one, but the team isn’t better because of it.

Meanwhile, the Jake Plummer signing looks worse with every interception.

Recently, Plummer’s former teammate, Sharpe, said the Plummer signing was the misguided product of a coach with a big ego who thought he could turn a mediocre quarterback into something more.

Many in Denver think Plummer (two touchdowns, nine interceptions in Denver’s recent 1-3 swoon) should go after this season. But Shanahan has shown no intention of going that direction, and Bowlen has supported the quarterback along with the coach.