MINNEAPOLIS — The Minnesota Vikings and wide receiver Adam Thielen have agreed in principle to a four-year contract extension valued at $64 million.

The Vikings announced the deal on Friday. Thielen’s agency, The Institute for Athletes, posted the terms on Instagram , including the potential through incentives to earn as much as $73 million over the life of the contract covering the 2021-24 seasons.

Thielen has two years left on the deal he signed in 2017, which easily made the Minnesota native one of the best bargains in the NFL after averaging 102 catches and 1,325 yards over the past two seasons. He was picked for the Pro Bowl both years, further enhancing one of the league’s best underdog stories.

He needed a pay-your-own-way regional NFL combine and a Vikings rookie tryout camp to make the practice squad in 2013 out of Minnesota State, an NCAA Division II school that offered him a mere $500 scholarship out of Detroit Lakes High School.

Thielen made the active roster in 2014 and contributed mostly on special teams for two seasons until becoming a starter in 2016.

The $16 million annual average value of Thielen’s new contract would rank him sixth in the league , behind Odell Beckham, Antonio Brown, Mike Evans, DeAndre Hopkins and Brandin Cooks, according to figures compiled by the sports salaries database Spotrac.com.