The 23-year-old faces leaders St Helens tonight having been one of the competition’s most impressive early performers.
He produced a remarkable 80m run last week to set up a try in the 38-6 win at Huddersfield Giants, racking up 156m, 29 tackles and the man-of-the-match in the process.
Such is his development, Rovers coach Tim Sheens has tipped the Pontefract-born player for eventual England honours. But what has been the secret to his recent success?
“I think I’ve been quite lucky with injuries to other players – not in a nasty way, obviously,” said Mulhern, while preparing to face Saints.
“But I’ve had a really good pre-season under my belt, too. That’s the first one I’ve had in maybe five years where I’ve not had an injury and I’ve just capitalised on that.
“Having the likes of (props) Scrutes (Nick Scruton) and Mose Masoe around, too, means I’m learning from them all the time.
“It’s as much down to them as it is to me; I’m a sponge at training, taking in as much as I can and it’s paid off so far. Hopefully, I keep on improving .
“It’s great to hear things like that from your coach that you’re doing well but I just keep trying to do that with my head down and, hopefully, I keep getting picked.”
Mulhern had been looking forward to a match-up tonight with Alex Walmsley – “I think along with Chris Hill they’re maybe the best two forwards in the league” – but the England prop is unfortunately missing for the foreseeable future due to surgery on his neck this week.
However, Saints are not short of options and, having seen their five-match 100 per cent winning start ended by Leeds Rhinos last Friday, are sure to be fired up.
“It’s just another opportunity for us really,” said Mulhern, who played just five games for Leeds before joining Rovers at the end of 2015.
“We’ll prepare the exact same way. We could get a result if we turn up with the same attitude as we had at Huddersfield.
“But that’s just one win. We can’t rest on our laurels.
“We have to be better again to get the win against Saints.”
Hull KR still just have two wins to their name from the opening six fixtures but Mulhern – a prominent player in their promotion from the Championship – said: “When you look at the actual quality in this squad its an unreal one.
“And we’re so close as a team that I think we’ll keep building and building. The first couple of weeks were a bit of a shock to us but we could have won in Catalans and at Leeds before that victory at Huddersfield.”
And a word on that run?
“The ball just ended up in my hands and I saw some open field so thought I’d pin the ears back and go for it,” recalled Mulhern.
“I managed to fend Danny Brough and get an extra kick. Jermaine McGillvary caught me but I got it to James Greenwood and he scored so I didn’t mind.”