DTH van der Merwe's surprise return for Glasgow Warriors' Pro14 semi-final against Ulster is "massive", says head coach Dave Rennie.

The Canadian, who scored the winning try in this fixture four years ago, was expected to be out for the season after a shoulder operation in February.

But Warriors' record try-scorer has recovered four weeks ahead of schedule and starts at Scotstoun.

"DTH is very experienced, really powerful and secure," Rennie said.

"He is massive for us."

The injured Niko Matawalu drops out of the Glasgow squad in the only change to the backline that started the thumping of Edinburgh last month.

Co-captain and flanker Callum Gibbins has recovered from concussion and Jonny Gray has overcome illness to feature, with Rob Harley shifting from lock to the blind-side flank, and Ryan Wilson and Tom Gordon dropping to the bench.

The match will be Warriors great Stuart Hogg's last at Scotstoun as the full-back prepares to join English Premiership side Exeter Chiefs next term, but not necessarily his last in Glasgow, with the final staged in the city's Celtic Park on 25 May.

"I think he's been outstanding, particularly over the last three games against tough opposition," Rennie, whose side have won eight games in a row, added.

"We know he has a lot of x-factor. He's given a lot of years' service to this club and the boys are desperate to send him out on a high.

"When there was a real drive to try to host the final here, there was obviously a lot of hope that we'd be part of that, so it's a motivating factor, no doubt. But what we know is that if we just put in a quality performance tomorrow, we've got a good chance ."

Ulster, coached by former Glasgow and Scotland assistant Dan McFarland, are boosted by the return of fit-again Ireland full-back Jacob Stockdale and wing Louis Ludik.

The duo's introduction to the backline are the only changes to the side that beat Connacht in the quarter-final, and join Robert Baloucoune in the back-three.

Ulster captain Rory Best and centre Darren Cave could play their final games for the province, with both retiring at the end of the season, although hooker Best will lead Ireland at the Rugby World Cup.

Centre Cave has been named on the bench by former Glasgow and Scotland assistant Dan McFarland and, if he comes on, he will equal Andrew Trimble's all-time Ulster appearance record of 229.

Glasgow Warriors: Hogg; Seymour, Steyn, Johnson, Van der Merwe; Hastings, Price; Bhatti, Brown, Z Fagerson, Cummings, Gray, Harley, Gibbins, M Fagerson.

Replacements: Stewart, Kebble, Rae, Wilson, Gordon, G Horne, P Horne, H Jones.

Ulster: Stockdale; Baloucoune, Marshall, McCloskey, Ludik; Burns, Cooney; O'Sullivan, Best, Kane, Henderson, Treadwell, Timoney, Murphy, Coetzee.

Replacements: Herring, Warwick, O'Toole, O'Connor, Reidy, Shanahan, Lowry, Cave.