Smith, who has not played since the start of May, trained last week but was held back for the New South Wales Waratahs match, which the Highlanders won 49-12 in Invercargill to scrape into the playoffs.
The co-captain's return is a big boost for the Highlanders' chances and brings them close to full strength, but winger Tevita Li has been ruled out with a knee injury and replaced by Sio Tomkinson.
With a total of six wins from the regular season, and one from their past four games, the Highlanders have no business being in the playoffs for some critics but they hit form at the right time against the Waratahs.
It will nonetheless take something special to topple Scott Robertson's Crusaders, who hammered the Highlanders 43-17 in Christchurch in their last meeting in April and have never lost a playoff at home in the history of the competition.
The nine-times champion Crusaders are also riding an unbeaten 28-game run at their Rugby League Park home.
The winner will play either the Wellington Hurricanes or the Bulls in the semi-finals.
(Reporting by Ian Ransom in Melbourne; Editing by Greg Stutchbury)
