In attempting to cover big numbers on three NFL games last week I lost twice and I'm upset. Not because I lost -- unfortunately, that happens much too frequently with my selections -- but because of the way the games were played.

Consider Indianapolis at the Los Angeles Raiders, for example. No one can blame Colts Coach Frank Kush for being conservative with his offense during the early part of the game. He knew he was overmatched by the Raiders' defense.

However, after getting a huge break -- Greg Pruitt fumbled a third straight punt return and Indianapolis scored after recovering on the Los Angeles one-yard line -- Kush still refused to open up his attack until the final few minutes. By then there was not enough time left to overcome a 21-7 deficit. But Kush went home happy, apparently, secure in the fact his offense had not been permitted to risk turnovers that might have led to a blowout.

The same thing happened Monday night in Miami, only differently. Coach Joe Walton and the New York Jets' offense gave the Dolphins' defense more than it could handle, on occasion, during the first 2 1/2 quarters. But once the Jets fell behind, 28-17, late in the third quarter, they refused to go after the big offensive play.

A quick-out to the sideline or a short dump-off pass over the middle won't succeed quickly enough to help a team that needs two touchdowns and has only six minutes left. Yet the Jets were willing to eat up the clock and maybe, if they got lucky, score one touchdown and lose by 28-24.

That's not how the game should be played. If a team is 11 or 14 points behind midway through the last quarter, it is expected to discard its conservative approach and make every effort to win. What a sad sight it is to see a few coaches and quarterbacks too timid to try.

The Las Vegas line this week lists Washington 10 1/2 over Minnesota tonight. Sunday finds Cincinnati at Cleveland rated even, Buffalo 3 over Indianapolis, Dallas 4 at Philadelphia, Denver 4 at Kansas City, Seattle 11 over Detroit, Miami 5 1/2 over the Los Angeles Raiders, the Los Angeles Rams 7 1/2 over New Orleans, the New York Giants 3 1/2 over the New York Jets, Pittsburgh 7 1/2 at Houston, New England 4 1/2 over St. Louis, San Francisco 13 at Atlanta, Green Bay 6 over Tampa Bay. Monday night, it's San Diego 2 over Chicago.

I will take an imaginary $500 on Washington and $250 each on the Raiders, Green Bay, Kansas City, New England, Detroit and Cleveland.

The Redskins, despite their 41-14 job on Buffalo, are not yet the devastating force they were the past two seasons. But they are getting healthier every week. The Vikings, in their last three appearances, yielded 35 points to Green Bay, 42 points to Denver and 34 points to Chicago. The Redskins should challenge 40, too. Give the 10 1/2.

The Raiders at Miami presents a beautiful matchup: the league's best defense against the league's best passing offense. Los Angeles won't shut down Dan Marino, but it might rough him up a bit, and that would be a new experience for the second-year pro. Conversely, the Raiders' offense continues to sputter and the Dolphins' defense is vulnerable to the run. The spread dictates the choice. Take the 5 1/2.

Green Bay's offense should have a good afternoon against the Buccaneers' badgered defense. The Packers, despite their loss last week in Detroit, have the makings of a good team for 1985 and should keep moving in the right direction. Give the 6.

Kansas City has played respectably in recent losses to the Raiders and the Giants. The Chiefs' defense has the potential to turn over the big play and Bill Kenney might enjoy more success than most people expect he will in throwing into the Broncos' secondary. Take the 4.

New England still has a good chance to make the playoffs. Neil Lomax has lost much of the confidence that marked his performance for the Cardinals over the first eight games. Give the 4 1/2.

Cleveland's defense rarely turns in a bad effort. The Browns, in fact, had been blown out only once, by San Francisco. They should gain revenge for the 12-9 loss in Cincinnati. The line is pick 'em.

Detroit is one of the best 4-8-1 teams in NFL history. Take the 11.