As a drafting expert who goes public with his selections and is rating a 290-pound offensive tackle with mended knees higher as a pro prospect than Billy Sims, Don Heinrich commands attention.

The former quarterback and coach sells "Don Heinrich's Scouting Report" for $6.50 (P.O. Box 17704, Seattle, Wash. 98017) and has established some credentials after 17 of his top-ranked collegians were picked on the first round last year.

One critic of the upcoming draft on April 29-30 has called it the worst crop of players since the process was started in 1936. Heinrich acknowledges this year's group is "skinnier" than in 1979 but discounts the attitude of some detractors.

"What happens," Heinrich said yesterday, "is that the same scout who is so enthusiastic about a player after seeing him in spring practice, becomes afraid to go out on a limb as autumn and the need for a decision approaches.

"By draft time the scout has reversed his field by saying this year's prospects are not as good as last year's and covers his previous enthusiasm by saying there's a great junior crop for the future.

"There are no superstars like Earl Campbell this year and no great quarterbacks, but how many are there any year? There are a lot of athletes who are going to make pro rosters and play next season."

Heinrich says his staff essentially does what pro clubs do. "We have pro scouts around the country who give us information on a confidential basis," he said.

"We do about five or six evaluations on a player and strike an average to determine our ratings, with 7 being perfect."'

One player rated 7 for this year's draft is offensive tackle Anthony Munoz of Southern California. Shane O'Neill, head of Henrich's staff, cautioned that it was a "pro-injury" rating, because Munoz has had three operations on his knees.

"I still think he will be drafted in the first round," O'Neill said, "even though he played in only USC's first regular season game and in the Rose Bowl. He is 6-foot-6 and 290 pounds and can run 40 yards in 5.0 seconds.

"He is the best collegiate offensive tackled since the New York Jets drafted Chris Ward from Ohio State in 1978 and Munoz is a better pass-blocker."

Most scouts have rated all-America guard Brad Budde of Southern California as the best player in the draft. Munoz, of course, did not receive all-America consideration sitting on the bench.

Heinrich gives Budde, Sims and guard Ray Snell of Wisconsin the closest ratings to Munoz, all 6.5.

Heisman Trophy winner Charles White of USC rated 5.8, tight end Junior Miller of Nebraska, 6.3; wide receiver Lam Jones of Texas, 5.7; fullback James Hadnot of Texas Tech, 5.5, and quarterback Marc Wilson of Brigham Young, 5.2.

O'Neill said, "The most intriguing challenge for the scouts' recommendations of linebacker George Cumby of Oklahoma, because he seems to be too small at 6 feet and 212 pounds, and would have to play outside. But he is so active -- all over the field -- teams will be tempted to go high for him."

Heinrich's report offers details to explain why some players are not rated higher. Quarterback McDonald of Southern California is lefthanded and rated behind Wilson.

"The highest-raters basically are on offense," O'Neill said, "in contrast to last year, when linebacker Tom Cousineau of Ohio State was the No. 1 pick in the whole draft. Then Buffalo lost him to Montreal of the Canadian League."