For the National Basketball Association, this is the draft that got stuck in the middle.

Most of the players who would have made Tuesday's draft among the best ever turned professional as underclassmen last year. And this year's top underclassmen, who could have bailed out this draft, decided to stay in school.

What this draft doesn't have are probably the second-, third-, fourth-, fifth-, sixth- and seventh-best players in college basketball, namely centers Patrick Ewing of Georgetown and Akeem Abdul Olajuwon of Houston; forwards Wayman Tisdale of Oklahoma, Keith Lee of Memphis State and Sam Perkins of North Carolina, and guard Michael Jordan of North Carolina.

What this draft does have is 7-foot-4 Ralph Sampson of Virginia. The Houston Rockets, by virtue of finishing with the worst record in the NBA this past season and winning a coin toss with Indiana, will take him with the first pick.

Although Sampson was often criticized for not having won a championship while at Virginia and for not being a factor at times in crucial games, the pros have nothing but good things to say about him.

"We had the Chamberlain era, the Russell era and the Jabbar era. And I think now we'll have the Sampson era," said NBA scout Marty Blake. "Ralph can do everything you want a player to do--score, rebound, block shots and pass. Most important, however, is that he's a cerebral player."

A number of teams are after Indiana's pick, including the Los Angeles Lakers, who have offered guard Norm Nixon and another player for it. If the Pacers keep their pick, they will most likely take 6-11 center Steve Stipanovich of Missouri.

After those two, the prospects are questionable.

"This would have been the best draft ever if all those guys hadn't come out last year," said Bullets General Manager Bob Ferry. "Now, though, it's nothing spectacular. It's good, but nothing out of the ordinary."

The first three picks last year (James Worthy by Los Angeles, Terry Cummings by San Diego and Dominique Wilkins by Utah) were all underclassmen, as were seven of the first 10 players picked and nine first-round selections overall.

Nine coaching changes among the 23 teams make it difficult to read this draft, but there is a consensus, at least, of who are the top six players. After Sampson and Stipanovich, the players expected to be selected next--not necessarily in order--are forwards Sidney Green of Nevada-Las Vegas, Dale Ellis of Tennessee, Antoine Carr of Wichita State and Rodney McCray of Louisville.

None are underclassmen. In fact, only six underclassmen applied for the draft: guards Ennis Whatley of Alabama, Byron Scott of Arizona State, Derek Harper of Illinois and Glenn (Doc) Rivers of Marquette; forward Clyde Drexler of Houston, and center Russell Cross of Purdue. None of them are franchise builders, yet all are possible first-round picks.

Other top players are point guards Greg Jones of West Virginia, Jon Sunvold of Missouri, John Paxson of Notre Dame and Rod Foster of UCLA; shooting guards Jeff Malone of Mississippi State, Darrell Walker of Arkansas and Dereck Whittenburg of North Carolina State; shooting forward Thurl Bailey of North Carolina State, and center Randy Breuer of Minnesota.

Green, 6-9, averaged 22.1 points and shot 55 percent last season, and also got 11.9 rebounds a game. He can run, shoot and jump. Ellis, 6-7, averaged 22.6 points and shot 60 percent, and is also considered a good defensive player.

Malone, 6-4, was the nation's third-leading scorer this past season and the fifth-leading scorer in Southeastern Conference history.

Foster is supposed to be the fastest player in the draft, Sunvold the smartest and Walker the best defensively.

The NBA's new collective bargaining agreement will affect only five teams this year--Los Angeles, Philadelphia, New Jersey, New York and Seattle. They have a team cap based on their payrolls this season. They can sign any rookie they pick with their own draft choices for whatever amount they want, even if it puts them over their cap. But if they trade for another No. 1 pick, they can pay that selection only $75,000, or adjust their payroll so paying him more does not put them over their cap.

Beginning with the 1984 draft, however, all first-round picks will have the option of signing for whatever the team that drafts him offers, or signing for $75,000 for one season and becoming a free agent the next.

For that reason, there was early speculation, due mainly to a misunderstanding of the collective bargaining agreement, that this was the last year of big money for rookies. But after the players and their coaches had a chance to study the agreement, they realized that a rookie will be in a better position next season because he will have an option and, if a team really wants him, it will be able to make roster adjustments to pay him whatever it takes.

Five teams--Houston, Indiana, Dallas, Washington and Cleveland--have two picks in the first round and four teams--New Jersey, Los Angeles, Boston and Atlanta--have none. No trades can take place between midnight Monday and the conclusion of the draft.

Washington area players expected to be drafted, other than Bailey and Whittenburg, are Michael Britt and Kenny Payne of the University of the District of Columbia; Mark Nickens, Ed Sloane and Juan Jones of American, and Sidney Lowe of North Carolina State and De Matha High School.