Captain Ben Stokes joked on Saturday that nobody really knows what they are doing when they inspect a wicket before a test match, as he continued to ponder England's final line-up for the fifth Ashes clash.

England named a 12-man squad for the clash on Friday with seamer Matthew Potts and spinner Shoaib Bashir likely vying for the one spot on the team - depending on what was expected from the pitch.

The latter was not as straightforward as it might seem, Stokes said.

"I looked yesterday and looked at it the day before as well," he told reporters before training at the Sydney Cricket Ground (SCG) on the eve of the start of the match.

"We try and act like we know what we're doing when we're looking down at the pitch and rubbing it and knocking it but no one really has a clue, to be honest."

From afar on Saturday, the SCG track looked to have a distinct tinge of green on it as the groundsmen ran the roller over it.

Victories in the first three matches of the series mean Australia will be raising the Ashes urn in triumph at the end of the test regardless of the result, but Stokes said it was still an important contest for England to win.

"This is a big game purely because we're walking out there representing England," he said.

"The Ashes, unfortunately for us, hasn't gone the way we wanted it to. But we've got one more game in a big series."

"Although we can't get the thing that we came here for, we've still got a chance to go out there and win a game of cricket for England."

Before Melbourne, England had not won a single test in Australia since early 2011 and the three previous touring squads arrived in Sydney for the final match utterly demoralised.

Stokes thought that would be different for his squad.

"The one thing that you don't want to see, and I don't think I will, is just sort of coasting through this game and seeing what happens," he said.

"We get to go home in eight or nine days' time but any thought of that can wait till then."
"It's about what we do over the next five days that's the most important thing, putting absolutely everything that we can into the game and giving ourselves the best chance of winning."