When the Raiders leave the field Sunday in Houston, no matter the outcome, they will have wrapped up the worst 100-game period in their 50-year history.

Now at 25-74, Oakland is assured of being worse during the last 100 than Detroit (27-72) or Cleveland — or even the first 100 of the Tampa Bay Bucs (35-64-1).

What’s more discouraging for longtime Raiders fans is the creeping realization there is no rational reason to expect the next 100 games to be much, if any, better.

Not because it’s impossible. The Cowboys and Colts, for examples, have delivered stunning turnarounds during the past 20 seasons.

But the Raiders, who have never been so bad for so long, are a unique breed of NFL cat. They have huge money tied up in their last three No. 1 draft picks, are magnets for drama and are operated by Al Davis, who has been unwilling to relinquish the amount of control required for dramatic change.

The Cowboys were revived by a dynamic new coach, Jimmy Johnson, and young players Troy Aikman, Emmitt Smith and Michael Irvin. The Colts came back with a wise coach named Tony Dungy and steady talents Peyton Manning, Marvin Harrison and Edgerrin James.

The Raiders vow a return to greatness behind coach Tom Cable, who was promoted from within, and such players as quarterback JaMarcus Russell, running back Darren McFadden and wide receiver Darrius Heyward-Bey.

Though it’s too early to pronounce this foursome unable, it’s not too early to dismiss comparison with the foursomes that brought Super Bowl titles to Dallas and Indianapolis.

Russell, struggling to establish his bona fides as an NFL quarterback, is a mess right now. His footwork, conditioning, decision-making, savvy, leadership — all of it is below the standards required to set an example for a winning team. They may be forced at some point to decide whether to fit a system around JaMarcus, who clearly is most comfortable in shotgun formation, or acquire a veteran QB who can sustain some offense.

McFadden always will make big plays, just not enough to justify being the first back taken in the 2008 draft. While great runners generally have wiggle or blast — or both — D-Mac has neither. He has plenty of talent and spirit, but his pencil-like legs, superb quickness and straight-ahead speed practically beg to be lined up in space.

Heyward-Bey’s biggest problem is that the start to his NFL career is not unlike most of his college career inasmuch as he’s on the field but unproductive. He appears to be what many scouts suggested before the draft, a sprinter in search of a football career.

While these three players are critical to the future, there is so much more to fix.

Poor drafting. The leadership core should come from the 47 players chosen from 1999 through 2004 — except only 45 aren’t on the roster as starting position players. Only cornerback Nnamdi Asomugha (2003) and guard Robert Gallery (’04) qualify.

Coaching quality and instability. Cable is the fifth head coach since ’02, and only Norv Turner lasted as long as two years. The last three — Art Shell, Lane Kiffin and Cable — would not have been hired for the position by any other NFL team.