The Suns (3-3) led after the first quarter but couldn't get much going after that and trailed by as much as 20.
Curry missed his second straight game after injuring his surgically repaired right ankle in Golden State's 101-97 win at Portland on Friday night. Projected starting center Andrew Bogut also sat out and his status is uncertain for the season opener in Phoenix on Oct. 31.
The Warriors fell behind early before rallying behind Jack and Barnes. The veteran guard and rookie forward combined for 14 points in the second quarter to help Golden State take a 55-46 lead.
Phoenix trailed by 14 midway through the third quarter, but pulled within 79-71 heading into the fourth before the Warriors pulled away.
Charles Jenkins drove past Morris and Wesley Johnson in the key for a three-point play that gave Golden State a comfortable 89-73 lead with 8:47 remaining.
Gortat, the only Phoenix player to start all 66 games in 2011, had 12 points and six assists in the first quarter.
The Suns close out the preseason at home against Denver on Friday, then host the Warriors on Oct. 31 in the opener for both teams.
Former Warriors center and 2012 Basketball Hall of Fame inductee Ralph Sampson was among those in attendance. Sampson now works for the Suns in their player development department.