Left arm chinaman bowler Shannon Tubb was an unlikely last-day hero for Tasmania as the Tigers clinched an innings victory over South Australia to lift them to second on the Pura Cup table with a round to play.

Tubb fought back after taking an early hammering to snare three crucial second-innings wickets and help dismiss SA for 242 today as the Tigers won by an innings and 32 runs.

Veteran paceman David Saker was superb in taking 5-53 as Tasmania dominated for the fourth straight day to gain the richly deserved win, which also boosted the Tasmanian percentage and put it ahead of Western Australia, which is on equal points.

Only a valiant innings of 138 from SA opening batsman Ben Johnson, lasting 418 minutes, forced the Tasmanians to stay in the field until an hour before the scheduled close.

It was the third century of the season from Johnson, who carried his bat on the two previous occasions, in a superb comeback after failing to earn a place in the side at the start of the summer.

SA started today at 2-66 and lost Ben Higgins (seven) and Chris Davies (three), both dismissed by Saker, in the opening eight overs to slump to 4-79.

Bradley Young shared a 61-run partnership with Johnson which soaked up 86 valuable minutes before Scott Kremerskothen bowled Young for 21 in the over before lunch.

Mike Smith joined Johnson and the pair batted for almost the entire session between lunch and tea, adding 64 runs in a partnership that looked as though it could deny the Tigers an outright win.

But it was Tubb, who conceded 35 runs in a loose five-over spell before lunch, who made the crucial breakthrough, having Smith caught behind for 31, the second highest score in the SA innings.

Tubb followed with the wicket of Graham Manou (zero) in his next over on his way to a critical spell of 2-6 from three overs leading into the tea break.

Tubb also claimed the wicket of Johnson, the ninth wicket to fall, which finally killed off SA's hopes, on his way to career best figures of 3-57.

Tasmanian captain Jamie Cox, named man of the match after his 174, said he was pleased with Tubb's comeback after his wayward early spell.

"We picked him to bowl these guys out on the last day, we took him off and we had to bring him back on at some stage," Cox said.

"He's turned it around brilliantly, he's had a real big turn in saying who won the game."

The Tigers play New South Wales in Hobart in the last round and an outright win will guarantee them a Pura Cup final berth for the first time since 1997/98, when they lost to WA.

© 2002 AAP