The former Wales Sevens star lines-up alongside Andrew Bishop in the Ospreys midfield and will be up against Grand Slam duo Jonathan Davies and Scott Williams.
Isaacs is the only centre on display to have not been capped by Wales but he is relishing the challenge ahead.
“I’ll be in the centre up against Jonathan Davies,” said Isaacs.
“I’m really looking forward to that battle — he’s a great player. He’s very powerful, a good footballer and very quick, so it will be a good challenge.
“The international backs we have in Wales at the moment are big boys. We’ll be up against two big, skilful centres in Scott Williams and Jonathan tonight. I’ll have to watch them carefully, but it’s important we concentrate on ourselves and what we want to try to do as a team.
“We’ll have plans to deal with some of their players, but we can’t worry too much about the Scarlets. We have to focus on our own game.”
The 25-year-old has established himself as a regular in the Ospreys set-up but has been utilised in the centre, on the wing, at full-back and at scrum-half for the region.
But he is more than happy to step into the midfield once again, to fill the void left by the injured Ashley Beck.
And the 25-year-old is looking forward to playing alongside Andrew Bishop in what promises to be a fiercely contested derby at Parc y Scarlets.
“I’ve played a few times with Bish and we seem to have a good partnership,” added Isaacs.
“Everyone’s aware of Bish’s defensive prowess, but we shouldn’t forget he’s a great attacker as well.
“Welsh derbies tend to be blood and thunder affairs, and we’re looking forward to the physicality of it.
“There’s a lot of good competition in the centre here, between Bish, Ashley Beck, Jonathan Spratt and myself.”
It will be the first cross-Loughor derby the Cardiff-born utility back has played in, although he has previously featured for Newport Gwent Dragons in Llanelli.
But he is relishing the prospect of playing in front of a red-hot atmosphere as the Ospreys look to kick-start a nightmare start to their RaboDirect PRO12 defence.
“I’m massively looking forward to it,” said Isaacs. “I’m really looking forward to experiencing the atmosphere of a packed Parc y Scarlets.
“It’s a passionate crowd down there and, as a player, that’s something that gets you going.
“I played against the Scarlets when I was with the Dragons but I understand how big a rivalry they have with the Ospreys.
“It’s something I’ve heard about a lot since being at the Ospreys, and I’m looking forward to being involved.
“A few of the Scarlets boys live near me, so there’s been quite a bit of banter flying around. It’s all been light-hearted but I’m sure that will all change when we’re on the pitch tonight.
“The Scarlets have started very well with three wins from three and they’ve been playing some good stuff, both up front and behind the scrum.
“We’re not in the best of form but we’ve been working hard in training to put right what we’ve been doing wrong in the first few matches.”
