"Try-scoring machine", was the term used by BBC Sport NI co-commentator Tony McWhirter as Ulster beat the Bulls 33-23.

Forget Damian Penaud, James Lowe or Mack Hansen - Tom Stewart is the man in form in European rugby.

The 22-year-old's hat-trick in the win over their play-off rivals in the United Rugby Championship on Saturday, which took him to seven tries in his last three games, moved him four touchdowns clear of any other player in the league.

Even more incredibly, his career statistics read as 15 tries in 20 Ulster matches. They are numbers most players can only dream of.

Stewart has been described as "an outstanding talent" by former Ulster and Ireland fly-half David Humphreys, while Springbok World Cup winner Duane Vermeulen said he is "a fantastic youngster".

While Grand-Slam winning Ireland have a settled trio of hookers in the form of Ulster team-mate Rob Herring and Leinster duo Dan Sheehan and Ronan Kelleher, Stewart has moved up to 'heir to the throne' and was involved in the Six Nations camp during the tournament.

He may not have made a squad but he was there watching and taking everything in as he continues to move towards a somewhat inevitable international debut down the line.

While he has yet to make his senior debut, although he was involved in Emerging Ireland's tour of South Africa in September, former Ulster back Louis Ludik believes he will be impossible to ignore for Ireland's World Cup squad if he can maintain his current form.

"For such a young guy he is playing some unbelievable rugby", Ludik said.

"He has been in the Irish set-up though the whole Six Nations. It was such a learning curve and you could see the smile on his face.

"He is doing incredibly well and scoring a lot of tries. It does help that Ulster's maul is probably one of their biggest weapons, but he capitalises on that and he makes very good decisions when he breaks off.

"His future is so bright and the world is his oyster at the moment."

Vermeulen, too, feels a step up with Ireland is only a matter of time.

"It's good for him, he got the call-up to the national squad," he added.

"Unfortunately he didn't play, but there is a bright future for him as a player and I hope he gets his opportunity pretty soon."

While the media and supporters will continue to get excited by Stewart, his head coach Dan McFarland was on hand to keep the youngster's feet firmly on the ground.

"He'll take his man of the match and his three tries, but he'll probably be at home tonight wondering why he dropped the ball twice coming off the back," he said.

"Tom has got high standards for himself. He's doing a good job but he has lots to work on too."

While McFarland is undoubtedly trying to manage expectation, he also raised a valid point about Stewart as the finished article.

While his general play was strong, there were a couple of unforced handling errors and some youthful exuberance led to Stewart conceding a couple of penalties in the second half.

It shows that he is far from the finished product, a rough diamond as such, but polishing his game will only help Stewart move to the next level.

Herring or Stewart - who starts in Europe?

Rob Herring, fresh from the try that secured Ireland's Six Nations Grand Slam against England, is set to return to the fold and, normally, would be nailed on to start in Saturday's European Champions Cup quarter-final away to imperious Leinster in Dublin.

However, the emergence of Stewart, and his subsequent form, has provided a headache for the head coach - who on earth starts at hooker? It's a nice problem to have.

"It's a really difficult one. Rob has been there, he has achieved a huge amount and is one of the senior players in this Ulster squad," added Humphreys.

"Tom has been so good and he brings a point of difference in his carrying.

"It will be interesting to see who he goes with. If you are picking on form I would start with Tom Stewart."

Ludik, however, believes McFarland will go with the 'been there and done it' approach of Herring for the inter-pro derby showdown at the Aviva Stadium.

"It's a difficult one but I think he will go for Rob with the experience he has," Ludik said.

"Tom brings a lot of x-factor. His carries are very, very explosive and sometimes Ulster do lack a bit of 'oomph' in their attack. He gets them over the line by breaking tackles.

"Whenever you play the Irish team, at the end of the day [a reference to the number of internationals in Leinster's team], you are going to need your best players on the pitch."