SA's Head makes timely runs in Shield

South Australia's captain Travis Head has made a timely half-century but the Redbacks are staring at defeat against Queensland in their Sheffield Shield game.

USMAN KHAWAJA. Picture: Robert Cianflone/Getty Images

South Australian captain Travis Head has boosted his Ashes credentials with a fighting half-century against Queensland in their Sheffield Shield match.

Head is unbeaten on 79 but his Redbacks are staring at defeat on the third day of play in Adelaide.

SA were 6-202 in their second innings at tea, a lead of just five runs.

Bulls skipper Usman Khawaja earlier put state before country with a selfless decision to enforce the follow-on at Karen Rolton Oval.

The decision risks robbing Khawaja of another innings while ensuring Head batted again in a fixture crucial to the Test ambitions of both players.

The duo are bidding for Australia's No.5 batting slot in the first Test against England starting on December 8.

After Marnus Labuschagne top-scored with 110 in Queensland's 299, the Redbacks crashed to 102 all out in their first innings.

But instead of opting to bat again, Khawaja made SA follow-on when 197 runs behind.

The decision was rewarded when the Redbacks lost 4-21 in a nine-over collapse just before lunch, with Bulls paceman Gurinder Sandhu taking all the wickets.

Sandhu later added another wicket to boast figures of 5-47.

Ashes outsider Alex Carey was among Sandhu's victims, out for three when caught at bat-pad but replays showed the ball struck only his thigh pad.

In SA's first dig, Bulls spinner Matt Kuhnemann collected career-best innings bowling figures - his 5-25 included the scalps of Head (eight) and Carey (two) on Wednesday.

Head's first-innings failure followed Khawaja making just four in Queensland's innings.