The Wales flanker reportedly faces a battle to earn Test selection with fellow countryman Justin Tipuric in red-hot form.
But Rowntree, who is also England’s forwards coach, has sung the praises of Warburton ahead of tomorrow’s clash with NSW Waratahs.
“I have been very impressed with Sam,” said Rowntree.
“He is very professional. He is certainly not showing any signs of stress or pressure.
“Like all the other players, he goes about his business. I have been really impressed with him as a person.
“He is a doer, and a lot of guys are following his lead in terms of his attitude to training, his diligence.
“It is not getting any easier in terms of selection. There are a lot of guys putting their hands up.
“We will get tomorrow out of the way, and then Tuesday (against the Brumbies), and then we will pick a Test team. That is the truth.”
The Lions lineout miss-fired at times during last Tuesday’s 64-0 victory over a Combined Country XV in Newcastle, and the Waratahs have been boosted by the inclusion of Dave Dennis, who has faced Warburton and Wales four times.
“Dave Dennis coming back in will bolster their lineout for tomorrow. He’s a good player, he has got some Test experience,” added Rowntree.
“We had a few issues in the lineout on Tuesday night. We dropped three from 16, but a lot of that was just personnel that hadn’t played a lot together.
“That’s what you get on a tour like this. You take it on the chin and move on.
“I actually thought they battled very well as a pack on Tuesday night. They didn’t really get enough credit for the performance they put in.”
