Early on in the trial that could end up forcing the NCAA to compensate its student-athletes, the plaintiffs have called on a renowned economist whose testimony could be key should they win.

According to ESPN, the legal team for former UCLA basketball star Ed O'Bannon called Roger Noll to the stand Monday. Noll is an economy professor emeritus at Stanford and he also spent all day Tuesday outline in exhaustive detail his theories as to why the NCAA will not pay its student-athletes.

Michael Hausfield is the lead attorney for O'Bannon, the lead plaintiff in a class-action lawsuit against the NCAA for not compensating student-athletes despite earning billions of dollars from lucrative TV contracts. If O'Bannon wins in the trial he has waited five years for, the NCAA could be forced to share their revenue in exchange for using student-athletes' names, images and likenesses.

One of Noll's main arguments was that the salaries of college coaches are taking away funds that could be used to compensate players. Since the 1980s, as NCAA Division I sports like basketball and football skyrocketed in popularity, so did the salaries of coaches. Among football coaches, compensation has risen about 500 percent over the last 30 years or so and in most U.S. states, they are the highest paid public official.

Noll also argued that teams in the five "power conferences" have plenty of money to spend and the gap between them and other schools is always expanding. He said schools in the ACC, Big Ten, Big 12, Pac-12 and SEC have long wanted to alter the NCAA bylaws to allow for better compensation to scholarship athletes.

Noll, who took the stand all day Tuesday, also made the argument the football players at Northwestern University made, that college athletics can be a job. Noll said student-athletes playing basketball or football at a power conference school are most likely trying to prepare for a professional future in that sport. This would mean they are not playing that sport as "hobby," but as a vocation.

Despite the lengthy testimony, Hausfield told ESPN Noll stuck to what he said he would. The economist will face cross-examination Wednesday from the NCAA's legal team.

"He focused on the basics," Hausfeld said. "The NCAA is known by all economists as a cartel, which creates restraints and harm. And the victims of that harm are athletes."

CLICK HERE to follow EPSN's live coverage on Twitter from the courtroom.

Thus far Wednesday, Tom Farrey has reported the NCAA is trying to discredit Noll's testimony by bringing up past articles and deposition the economist has given. The NCAA is also arguing that the plaintiffs' data is only based on a select group of coaches, but Farrey also noted the NCAA is not showing a clear direction in its cross-examination.