St Kilda named courageous midfielder Luke Ball and Collingwood recalled skipper Scott Burns in significant boosts for Saturday night's AFL semi-final.

The Saints tested Ball's fitness behind closed doors at Moorabbin, before naming him to return for what would be his first game since tearing his hamstring during the Saints' round-18 win over Port Adelaide.

His presence will be crucial in the do-or-die clash, given his ball-winning and tackling ability, two areas in which the Saints were sadly lacking during last weekend's disappointing loss to Geelong.

The Saints added further grunt with the inclusion of hard-nosed youngster David Armitage, who forced his way back for his first senior game since round 17 after a series of strong performances in the VFL.

Xavier Clarke, who managed just eight disposals against the Cats, and forward Charlie Gardiner were the two players dropped.

The Saints retained utility Jason Blake in their side, despite him hurting his thumb and shoulder against Geelong.

Burns, who has missed the Magpies' past two games with a calf strain, demonstrated his readiness to return by training strongly in the Magpies' main session on Wednesday.

He was included at the expense of Rhyce Shaw in the only change for the Magpies.

Shaw had played the club's past two games, after missing the previous four, two of them as a result of a club-imposed suspension.

Tall defender Simon Prestigiacomo kept his spot despite concerns over a shoulder injury sustained against Adelaide last week and selection pressure from fellow veteran backman Shane Wakelin.

Wakelin was named as an emergency, as was Shaw, along with young key forward Ben Reid, who has not played since injuring his foot in round 13.

The Western Bulldogs added some defensive cover for Friday night's semi-final clash with Sydney, with young tall Stephen Tiller replacing midfielder Farren Ray in their only change.

Tiller has played only nine previous games this year and 14 in his career, but the Bulldogs are wary of the danger posed by Swans forwards Barry Hall, Adam Goodes and Ryan O'Keefe.

"If you look at the Swans forward line, it's very talented with some height that's very agile," coach Rodney Eade said.

Ray was dropped after a poor performance in last weekend's big qualifying final loss to Hawthorn.

But Eade said the club had not wanted to make wholesale changes at this time of the year despite their disappointment with the style in which they lost to the Hawks.

He admitted the form of experienced forward Scott Welsh had caused some concerns among the match committee, but they had faith he would bounce back.

"He's kicked five (goals) against them last time and then there's probably a game or two where he hasn't kicked a lot of goals, but he's had 17-18 possessions in a different role, playing further up," he said.

"His last two or three (games) have been down, there's no doubt about that.

"(But) he has finals experience, he's a talented player, he can kick goals and he can take marks."

Welsh, who played in North Melbourne's 1999 grand final win is one of only two Bulldogs with premiership experience, along with Jason Akermanis, who was part of the Brisbane team that won three flags from 2001-03.

The Swans named the same 22 that beat North Melbourne last weekend, but coach Paul Roos said there might yet be a change ahead of Friday night's match.

"Craig Bird trained well and Luke Ablett is a little bit sore, but we expect Luke to play," Roos said.

"So there may be a late change, but probably as named."

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