Here's the list of UFA' bigs that are left :
Troy Murphy : 32 years old, 6'11 tall. Earned $854,389 last season with the Lakers. Can shoot the 3 point ball and perimeter shots. He turned us down back in 2010 for Boston, we know how that worked out

Kyrylo Fesenko : 25 years old, 7'1 tall. Earned $435,000 last season with the Pacers. He also turned down us last off-season and chose the Warriors over us, but the Warriors changed their minds and rescinded their offer to him. We didn't pursue him again and he was then picked up by the Pacers.
Jason Collins : 33 years old, 7'0 tall. Earned $854,389 last season with the Hawks. Career averages of 4 ppg, 4 rbg, 0.5bpg in 21 mins per game.
Hamed Haddadi : 27 years old, 7'2 tall. Earned $1,300,000 last season with the Grizzlies. 4 years NBA experience, career average of 2 ppg, 2rbg, 0.5 bpg in 6 mins per game.
Ryan Hollins: 27 years old, 7'0 tall. Earned $248,048 last season with the Celtics. 6 years experience, career averages of 4 ppg, 2 rbg, 0.5 bpg in 13 mins per game.
Joel Pryzbilla : 32 years old, 7'1 tall. Earned $420,304 last season with the Blazers. Career averages of 4 ppg, 6 rbg, 1.4 bpg in 20 mins per game.
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Those are it.
I say Riley immediately needs to go after Joel Przybilla.