Barring an unforeseen change of events, Phoenix Suns center Alex Len is planning to sign the team's $4.2 million qualifying offer before training camp, clearing the way to become an unrestricted free agent in 2018, league sources told ESPN.

The Suns open camp on Tuesday at Northern Arizona University in Flagstaff.

Phoenix Suns center Alex Len is expected to sign a qualifying offer from the team before training camp begins on Tuesday. Barry Gossage/NBAE via Getty Images

Len, 24, the fifth overall pick in the 2013 NBA draft, has spent the summer as a restricted free agent.

Len, a skilled 7-footer, investigated offer sheets and sign-and-trade proposals, but none made sense with the possibility of free agency next summer. The Suns are preserving salary-cap space in 2018 without signing him to an extension now, but do risk losing Len for no compensation.

With Len signing a $4.2 million qualifying offer, Phoenix would enter the season with $14.3 million in salary-cap space. Len will have veto power over a trade. If traded, he would lose his Bird rights in contract negotiations.

Phoenix wants to study's Len's progress in the 2017-18 season before committing to a long-term, lucrative contract extension to him. Len has started 80 games over the past two seasons, including 34 in 2016-17 when he averaged eight points, 6.6 rebounds and 1.3 blocks a game.