Carsen Edwards agrees to four-year pact with Celtics

LAS VEGAS — Rookie guard Carsen Edwards agreed to a four-year contract with the Celtics that will pay him more than $4.5 million in guaranteed salary over the course of the deal, according to a league source. The first three years of Edwards’s deal are fully guaranteed, with the Celtics holding a team option in the fourth season, according to the source.

It is unusual for teams to fully guarantee three seasons for second-round picks, but it is indicative of the Celtics’ confidence in Edwards, the 33rd overall pick of last month’s NBA Draft. He has been the Celtics’ top offensive player during the Las Vegas Summer League, averaging 18 points on 52 percent shooting in just 23 minutes per game. He also is averaging 2.8 rebounds and 1.5 assists per contest, helping Boston to the No. 1 seed in the summer league playoffs.

“I know [the Celtics] just want me to improve,” Edwards said earlier this week. “The Celtics team wants me to improve and be consistent in every game. Just focusing in on being a good defender and making good decisions. Just trying to be consistent.”

Last season, Edwards averaged 24.3 points per game as he guided Purdue to a regional final in the NCAA Tournament.

The 6-foot-1-inch guard is the last of Boston’s four draft picks to agree to a deal. Romeo Langford and Grant Williams automatically received slotted guaranteed contracts as first-round picks, and second-round pick Tremont Waters recently agreed to a two-way contract.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.