Bentley, an off-season recruit from St Helens, was sin-binned in the first half of Friday’s 24-6 win at Headingley.
The second-rower spent 10 minutes on the sidelines following a high tackle on Thomas Minns after the Trinity centre – a former Rhinos academy player – had caught a kick.
That was Bentley’s third card in just eight games for Leeds – following a red against Warrington Wolves and yellow at Castleford Tigers – and he has already been suspended for six matches this season.
He will hear today if the RFL’s match review panel have charged him over the latest incident. Speaking straight after the game, Smith said: “I haven’t seen the up close version of it.
“I’ve only seen the slightly wider angle and it didn’t look like it had too much in it, from that angle.”
Asked whether Bentley needs “reining in”, the coach added: “It is a fine line.
“It is a combat sport [and] it is a matter of managing your own thoughts and having that level of competitiveness that’s appropriate for the moment.
“James is a young man with big aspirations and drive to do well and he needs to continue to work on when to do what.”
Despite the sin-binning, Bentley had his best game for Leeds, scoring the first two of their four tries. Smith said: “I thought he had an excellent game.
“He had a good balance of competing hard and being very effective with what he did.”
Another talking point was the lack of game time given to replacement hooker Dwyer, who played only 10 minutes in the second half. Dwyer is out of contract this autumn and has been linked with a move to St Helens.
“Kruise [Leeming] had an outstanding game, I thought, at dummy-half,” Smith said.
“We put Brad on there to speed the game up for a little bit, which he did.
“He had four or five good carries that kept them honest and the plan was always to finish with Kruise at the back end.”