With their best attacking weapon Rene Ranger almost a bystander on the wing, the Blues went into halftime trailing by 10 - 19, having faded after scoring the opening try to halfback Jamison Gibson-Park.
The game stuttered along in a sparsely populated Free State Stadium until the final quarter when the Cheetahs powered home through tries to replacements Sarel Pretorius and Boom Prinsloo. The Cheetahs were aided by a seven-from-seven goalkicking effort from Riaan Smit. The lively Springboks wing Willie le Roux was a roving danger who switched to a more central role, although like the game itself his good intentions went astray now and then.
Williams, the veteran lock who retired from test rugby this year, refused to speculate on his own future next season when Kirwan will have to start again in more respects than he may have wished.
Kirwan's supposed Blues revolution, initially a breath of fresh air after the disasters of Pat Lam's reign, has stumbled and looks in need of a major overhaul itself, although the Blues did promote exciting new backline talent to higher levels.
Williams said: "They (the Cheetahs) outclassed us. They strangled a team like us. We had a great year but unfortunately we've fallen short."
The Blues face a daunting final assignment at Eden Park against the champion Chiefs, who will be smarting after a major defeat against the Crusaders and desperate to maintain a good seeding.
Cheetahs 34: Phillip van der Walt, Sarel Pretorius, Boom Prinsloo tries; Riaan Smit 5 pen, 2 con.
Blues 13: Jamison Gibson-Park try; Baden Kerr 2 pen, con.
Halftime: 19 - 10.