The Matildas custodian makes her long-awaited return to the finals with Canberra United in Sunday's semi-final against Sydney FC at McKellar Park.

Williams was an integral part of Canberra's inaugural championship in 2011-12, but missed last season's triumphant campaign recovering from a torn ACL.

Her class was there for all to see on the international stage, helping Australia charge to the quarter-finals at last year's women's World Cup in Canada.

The next assignment for the Matildas is a brutal Olympic Games qualifying tournament where they will play five games in 10 days in Osaka from February 29 to March 9.

Expectations will be raised after Australia's men's team, the Olyroos, failed in their bid to qualify for Rio.

Williams has missed two Canberra United games this season while on international duty with the Matildas.

"As soon as Canberra United and the W-League is over, it's straight into camps and the national team commitments," Williams said.

"There's always been one eye on the W-League and one eye on the national team.

"Coming out of season right back into a full-on program then a tournament is going to help us."

The Matildas face a difficult task to qualify, with six teams battling it out for two spots.

"This will hopefully be third time lucky qualifying through Asia for the Olympics," Williams said.

"If we do qualify, that's going to be a big feat in itself, and something we're going to look forward to and try our hardest.

"Just like the World Cup, we can beat anyone. First things first, but hopefully we have the drive and the talent to take it all the way."

Canberra are unbeaten in their past nine games, their rock-solid defence playing a major role.

They have conceded just eight goals in 12 games this season, four of those coming in a 4-2 loss to unbeaten premiers Melbourne City.

After that, Canberra kept five clean sheets in a row, Williams playing the first four of those before back-up 'keeper Melissa Maizels filled in for the fifth.

"What changed was the motivation and belief we had," Williams said.

"Things that may have cost us errors and goals were easy fixes.

"It wasn't necessary something difficult or really problematic, but we were able to work on that throughout the week and fix those issues."

Williams has also agreed to return to the US, signing with the Houston Dash where she will team up with Canberra defender Ellie Brush.

"It's pretty exciting to be back in the league," Williams said.

"This is my first full season playing back after my knee and I'm excited to play with some familiar faces."

Canberra put the finishing touches on their preparations with a light training session at McKellar Park on Saturday morning.

They have their full squad available for the clash with the Sky Blues apart from central defender Emma Checker, who is out for the rest of the season with a torn ACL.

Canberra are aiming for their third straight win against the Sky Blues this season.

A dominant 3-0 win at home, when both teams were without their Matildas stars, was followed by a narrow 1-0 victory on the road.

The second semi-final between Melbourne City and fourth-placed Brisbane Roar will be played at AAMI Park on Monday.

SUNDAY: W-League semi-final: Canberra United v Sydney FC at McKellar Park, 2pm. Tickets available from the gate. Live on ABC TV and Fox Sports 505.

Canberra United squad: 1. Lydia Williams (gk), 2. Catherine Brown, 3. Julia De Angelis, 4. Kendall Fletcher, 5. Jenna McCormick, 6. Caitlin Munoz, 7. Ellie Brush, 10. Grace Maher, 11. Michelle Heyman, 12. Emma Kete, 13. Nicole Begg (c), 14. Ashleigh Sykes, 16. Tegan Riding, 17. Veronica Perez, 18. Rebecca Kiting, 19. Nickoletta Flannery, 20. Melissa Maizels (gk)

Sydney FC squad: 1. Michelle Betos (gk), 2. Elizabeth Ralston, 4. Sunny Franco, 5. Jasmyne Spencer, 6. Teresa Polias (c), 7. Nicola Bolger, 9. Princess Ibini, 10. Renee Rollason, 11. Natalie Tobin, 12. Olivia Price, 14. Alanna Kennedy, 15. Teigen Allen, 17. Kyah Simon, 18. Sham Khamis (gk), 19. Leena Khamis