He is aiming to secure a place in the squad for this year's tournament in New Zealand.
Morrison missed the RBS 6 Nations with a knee injury butb has been included as one of five changes, with a further positional switch from the March defeat of Italy, in the team to play at Murrayfield.
The 28-year-old Glasgow Warriors centre missed the final cut for the 2007 tournament and is determined to make amends and be one of the 30 players named in head coach Andy Robinson's World Cup squad on August 22.
Morrison said: "He (Robinson) has 20-odd names (in mind), but he gives nothing away.
"He keeps his cards fairly close to his chest - you can't really read too much into it.
"I think it's quite a positive thing that I'll be playing in this game and I'll take it one step at a time.
"I'm desperate to go to a World Cup, given I missed out on the last one.
"It still hurts, but I've learnt a lot since then. I've become a far more mature player, I've got a lot more international experience and I think I'm in a far better place to go to the World Cup and do well than I was last time round.
"I'll get the opportunity to show what I can do on Saturday and hopefully it goes well."
Morrison's inclusion in the team for the first of two World Cup warm-up Tests resulted in Sean Lamont being switched to the wing and Simon Danielli dropping out of the matchday squad.
In the forwards, Ross Rennie will make his first Scotland start at openside flanker in a new-look back row, with Johnnie Beattie to start at number eight and Alasdair Strokosch at blindside flanker.
Jim Hamilton will start at lock alongside Richie Gray and with Alastair Kellock, Scotland's skipper during the Six Nations, named on the bench, Rory Lawson will captain the team.
Lawson was Scotland captain in last November's wins over South Africa and Samoa, when Kellock was out injured.
Robinson has chosen his World Cup captain, but is yet to reveal his leader.
The head coach said: "Al's not starting, so Rory, who is part of the leadership group, leads the team.
"I know who my captain will be (at the World Cup), but I've not informed the players yet."
Kellock was one of five players withdrawn from club service by Robinson in preparation for the World Cup.
Gray, Ross Ford and Allan Jacobsen have all been named in Saturday's team for their first competitive action since the Six Nations, but John Barclay has been left out of the matchday squad.
Barclay has been a proven performer for Scotland since making his debut in the 2007 World Cup, but his absence gives Rennie a chance to stake his claim.
The Edinburgh flanker, who is set to win his seventh cap, said: "It's really good for me to be given an opportunity - I've got to try and perform well and to perform for the team.
"I don't want to think about the World Cup too much now. I've got to focus on this weekend and try and get things right there.
"If I can do that, hopefully the rest will look after itself."
Robinson is keen to see how the back row and centre combinations perform as Scotland seek to fine-tune preparations for New Zealand, but there are also places to be claimed.
Dan Parks has not been selected, with Ruaridh Jackson chosen to start at fly-half and Robinson assessing his options.
Edinburgh duo Greig Laidlaw and Chris Paterson, who, if selected, would become the first Scot to play in four World Cups, will also be considered as back-ups to play at number 10.
Paterson will on Saturday win his 105th cap, playing at full-back, while Laidlaw can play at scrum-half and fly-half.
Two uncapped players - 21-year-old Edinburgh back-row forward David Denton and 23-year-old Bath full-back Jack Cuthbert - join Laidlaw on the bench on Saturday.
The Edinburgh half-back provides cover for Lawson at number nine as Mike Blair (ankle) and Chris Cusiter (calf) have suffered injuries of late.
Hugo Southwell and Fergus Thomson have already been lost to injury from the initial 40-man squad, so eight further players will be dropped from the squad before the final party is named.
Scotland's World Cup campaign begins against Romania on September 10 in Invercargill.
Full team: C Paterson (Edinburgh); N Walker (Ospreys), J Ansbro (London Irish), G Morrison (Glasgow Warriors), S Lamont (Scarlets); R Jackson (Glasgow Warriors), R Lawson (Gloucester); A Jacobsen (Edinburgh), R Ford (Edinburgh), G Cross (Edinburgh), J Hamilton (Gloucester), R Gray (Glasgow Warriors), A Strokosch (Gloucester), J Beattie (Glasgow Warriors), R Rennie (Edinburgh).
Replacements: D Hall (Glasgow Warriors), A Dickinson (Sale Sharks), A Kellock (Glasgow Warriors), D Denton (Edinburgh), G Laidlaw (Edinburgh), N De Luca (Edinburgh), J Cuthbert (Bath).
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