Marshall was impressive during Ulster's season opening 32-32 draw with Scarlets in the GUINNESS PRO12, Andrew Trimble's late try sealing a draw for the Irishmen.
And while Pienaar is on Springbok duty Marshall, who has three Ireland caps to his name, is desperate to make the most of his opportunity.
"Without being disrespectful I don't really care who is at Ulster rugby in terms of scrum-half, I just want to play every game," he said.
"Everyone is competing for a place and from my point of view I just want to kick-on with every opportunity I get, and enjoy my rugby.
"No matter who you are you have to play well at your club and for me I have played a few times for Ireland, but have not been in the hunt at all last season, so I'm not honestly thinking about it.
"We have a really exciting squad this season. I know a lot of people have said there has been plenty of changes behind the scenes, but things are looking good."
There was some bad news for Ulster at the start of this week, however, as their young international star Iain Henderson could be out until the New Year after hip surgery.
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