Tahlia McGrath answers the call when it matters to drive Australia to knock-outs

Australia's remarkable depth came to the fore yet again on Saturday night in a comfortable victory over hosts South Africa in Gqeberha to storm into the T20 World Cup semi-finals and, for Tahlia McGrath, it was a "relief".

It had only been seven innings since McGrath's last international half-century - she scored 70 not out in the second T20I against India in December, which India won in a Super Over - but, given that Australia's batting has gone largely unchallenged and with the range of bowling options available to them, she had felt like a "specialist fielder" for this World Cup campaign. That was until her 33-ball 57 which handed Australia a six-wicket victory over South Africa with 21 balls to spare.

Australia were without Alyssa Healy, who is expected to be fit for the knockout stage - she missed the match against South Africa as a precaution, with a problem in her left quad, having recently returned from a calf injury. So when Beth Mooney, also keeping wicket in Healy's absence, stand-in opener Ellyse Perry and Meg Lanning all fell cheaply, McGrath got her chance. And she took it, as so many of Australia's players tend to do when their time comes, much to the frustration of their opponents.

"It's a big relief," said McGrath of her knock. "I haven't been batting overly well and I've lacked some time in the middle, so I was a bit nervous to start off with. It's been nice watching the batters at the top of the order do their thing, but also nice to get an opportunity tonight.

"That's absolutely our biggest strength, that we've got so many options. So many players can play different roles and it seems to be someone different sticks their hand up every time. We're all in really good form at the moment with the bat, with the ball. We've got a really strong squad over here, so we go into those semi-finals full of confidence.

"I've been a specialist fielder the last couple of games, but this is my first T20 World Cup. I'm loving it. I love every chance I get to put on an Aussie shirt. I knew I was going to have an opportunity where the team needed me and I had to be ready."

Medium-pacer McGrath had conceded 13 runs off her solitary over in the tournament, as Australia thrashed New Zealand in their opening match, with the pitches largely favouring Australia's spin stocks, which are so vast that Jess Jonassen has sat out the last three matches. McGrath was again not called upon with the ball as they shared their six wickets among five bowlers, with legspinner Georgia Wareham picking up two. It was Wareham who had stepped up in Australia's second match, against Bangladesh, replacing Jonassen and taking 3 for 20 to lead another comfortable victory.

For their part, South Africa didn't' score nearly enough despite a bright start from Tazmin Brits, who struck 45 of 36 balls to help them to 70 for 1, before she was the first of Wareham's two wickets, the other being the dangerous Chloe Tryon. But with no other batter passing 20 and Marizanne Kapp falling for a second-ball duck in her first international appearance at her home ground, a hugely supportive atmosphere fell flat - Australia were just too good.

When Kapp had Perry caught feathering to Tryon at slip, Kapp's response was a clenched jaw and an approving wag of her index finger. Then Nonkululeko Mlaba bowled Lanning as she tried to scoop and deflected the ball off her glove onto her stumps and Kapp pinned Mooney on the toe, sparking the crowd of 8,367 back to life, in full voice and waving their mobile phone lights in the air.

But needing 85 off 78 and with star allrounder Ashleigh Gardner and McGrath at the crease, Australia got the job done. McGrath brought up her fifty off 29 balls by piercing the off-side field with an elegant cut for four, bookended by drives through mid-off and extra cover for three consecutive boundaries. She fell on what turned out to be the penultimate ball of the match with Australia needing four more runs. So Grace Harris, who on Thursday had been the one to step up with two crucial wickets and a stunning catch as Australia defeated Sri Lanka, hit the winning runs in emphatic style, clubbing the first ball she faced to the backward square leg boundary.

Sune Luus, South Africa's captain, described the performance as "classic Australia" and said she would now have one eye on New Zealand's match against Sri Lanka on Sunday. South Africa are third in the group behind Sri Lanka, to whom they lost the opening match. They must defeat Bangladesh and hope Sri Lanka lose to New Zealand to qualify for the semi-finals.

"I think if you're going to look too much into a team like Australia, you're going to get lost in what they do," Luus said. "They're obviously a well-oiled machine, a lot of strengths and not a lot of weaknesses, but it's important for us to focus on what we do best. So the focus was really mostly on us, where our strengths lie and what we can do better against the attack we're facing.

"The loss against Sri Lanka wasn't ideal, but that's cricket, that's World Cups. We're very much focused on the next game, anything can still happen in this tournament, so I think we're very much hopeful that tomorrow New Zealand can play a good game, but not too good."