The Harlequins forward has twice been involved in incidents during this season’s tournament.
In England’s Six Nations opener against Ireland he became embroiled in an exchange with flanker Peter O’Mahony, and in the France game eight days later he was reminded of “rugby’s values” by match referee Nigel Owens after slapping Les Bleus forward Arthur Iturria on the head.
Speaking last week about the Iturria incident, Sinckler said: “I don’t condone what I did, but they didn’t show the full replay of what actually conspired. I didn’t just smack him on the head. There was stuff that happened before.
“I am not perfect, and I have learnt from it.”
Sinckler, who was coached by Gatland on the 2017 British and Irish Lions’ New Zealand tour, will start against Wales in Cardiff.
Gatland said: “I think the thing with Kyle, there is no doubt he’s a very good player in terms of his carrying, scrummaging and work-rate.
“There is a challenge sometimes with his temperament. He’s aware of it. Other players are aware of it. We’ve already seen in the Six Nations that he has been involved in a couple of incidents.
“Hopefully, we don’t get dragged into that on Saturday. Emotionally, he can be a bit of a time-bomb. I am not saying anything that people aren’t aware of.
“Look, we won’t be going out there trying to antagonise him, because that’s not in our make-up. We will just go out there and play.
“Hopefully, he goes out and has a good game and is able to keep his emotions in control, because that’s a big challenge for him.”
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Watch: Wales head coach Warren Gatland on England test
Gatland has also underlined the need for his players to remain disciplined in a game that will see this season’s remaining two unbeaten Six Nations teams go head to head.
“There is no doubt it’s going to be incredibly physical with a lot of passion involved,” he added. “Discipline is going to be paramount.
“I want my players to bring that physicality and be emotional, but I don’t want them going over the top, losing their edge or getting involved in foul play.
“One thing I can’t stand about the game is foul play. We want to play tough and hard, bring as much physicality as we can, but playing to the laws of the game.
“This has become a really big game for both of us, not so much for the Six Nations, but building for the rest of the year, World Cup plans and preparations and for Japan.
“They are a quality side. They have strength in depth. It is going to be a great challenge, and we are excited to play at home against a team who are really on form at the moment.
“Win this game, I think it sets you up mentally as much as anything for the rest of the year.”
Gatland will step down as Wales boss after the World Cup, and he has been linked with possibly becoming Jones’ eventual England successor.
“Just speculation,” Gatland said. “I think my name has been mentioned with half a dozen jobs.
“My plan is to see out the rest of the year, and then see what else is available.”
And asked about Jones’ assertion that Saturday’s game is the biggest in the Wales players’ lives, Gatland added: “He’s taking the mick. He’s talking about us.
“It’s a big game, but it’s not the biggest game we’ve played in. It’s only against England!”
Watch: Eddie Jones talks to RugbyPass ahead of Wales
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