A calf injury may scupper Josh McGuire's chances of lining up for the Maroons in the State of Origin series opener on June 5.

McGuire left the field after 28 minutes of his side's 28-14 win over the Titans at 1300Smiles Stadium on Friday night and did not return.

His initial disappointment at sustaining the injury was there for all to see as he left the field. Scans in the coming days will provide a clearer picture.

With grade two calf strains still sometimes needing as many as six weeks to fully heal, McGuire will be hoping he only sustained a grade one injury. That would likely result in between one and three weeks on the sidelines.

Cowboys coach Paul Green was reserved in his discussion of McGuire's injury.

"Hopefully it's not too bad. It's probably just a low-grade calf strain so we'll assess it over the next couple of days and get a better reading on it," he said.

"Until we know the extent of it I can't really speculate too much."

McGuire's injury aside, the night was a pleasing one for the Cowboys.

Jason Taumalolo looked as though he hadn't missed a beat in his return from the knee injury suffered in round two.

"Considering how long he's been out and the minutes he knocked out tonight I thought he was enormous for us," Green said.

"I think credit to the medical staff too, he's come back at the shorter end of what was originally said. He came back and didn't miss a beat."

Taumalolo's return resulted in highly-skilled prop forward Joh Asiata moving to five-eighth. As he has done on the past, he handled with switch the aplomb.

"I thought he was really good. That was a big play for him to come up with. He read the play really well, saw the space, left foot grubber kick, he's a right footer, so a big play.

As for playing in the halves long-term, Green said: "We'll see. He certainly did a great job for us tonight."

The Cowboys next face South Sydney in Brisbane as part of Magic Round on Sunday. Green is a fan of the new concept.

"I'm looking forward to it. Having all the teams in the one place I think it will build a bit of interest," Green said.

"I know in previous years the Nines have always had a good buzz around it having everyone in town, so hopefully it's got that similar feel."