After being kept out for over two months with knee ligament damage, the 23-year-old completed 80 minutes but could not prevent Ulster going down 22-13 to GUINNESS PRO12 rivals Scarlets in Europe last weekend.
The injury came at the worst possible time for Marshall as he missed Ireland's successful autumn campaign and lost ground in the battle for his club's No.12 jersey to talented centres Stuart Olding and Stuart McCloskey.
Yet with Marshall sure to be heavily involved in a busy period for Neil Doak's side, the Ireland international is determined to seize the opportunity, starting with a visit to the high-flying Ospreys on Saturday.
"I was delighted just to get back on the field," Marshall told The Irish Times.
"Getting through the 80 minutes is a personal victory in the context of the season so far and I was reasonably happy with my performance but that was a minor consolation given that the team lost.
"There were one or two wee mistakes and a little bit of rustiness too but it's great to be back.
"Given our injury list this season I had a few boys to keep me company in the gym. It made it a wee bit easier when rehabbing but the other side of that was the frustration in having to sit and watch matches.
"There was only so much I could do because of the knee but I was aware that my game had to improve and get stronger in various areas if I was going to fight for my place.
"There is plenty of talent (at inside centre) with Stu Olding and Stuart McCloskey. You can see that in what they have done."
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