As the Roosters ran riot in the first half to open up a 28-0 lead at the break Mitchell was one of the major beneficiaries, scoring two tries in the first 40 minutes before sealing the 32-18 Telstra Premiership win with the final try of the night.
Robinson was unaware that Mitchell had even scored the first hat-trick of his young career and said the decision to move him into the centres was made just two days after the 2016 season came to a close.
After scoring 10 tries in 16 games at fullback last season the freakishly gifted athlete looked set for a lengthy tenure as the Roosters' custodian but the arrival of Michael Gordon in the off-season saw Mitchell moved to left centre.
He caused the Titans defence issues with virtually every touch in the first half yet despite his three tries and seven tackle busts only received a muted accolade from his coach.
"They're there to finish those tries and score those tries," was Robinson's blunt assessment.
"People are going to value that but I didn't know he'd scored three until someone reminded me after the game.
"We're looking at the other stuff that was good and it wasn't a bad game from him. It was a pass mark from what we want from our centres but it's a good start to our season."
Mitchell declined to be interviewed after the game but his partner on the left edge, Roosters winger Daniel Tupou, believes they merely scratched the surface of what's possible in their first game together.
Tupou was among the Roosters' best with some damaging runs (210 metres) and six offloads and says he has to be alert at all times as to what Mitchell may produce.
"It's a good start, especially for us two as a new combo," Tupou told NRL.com.
"We've still got stuff we need to work on but in the meantime we're happy with that start and we'll just get ready for next week.
"I've just got to adjust to whatever he does because he can play and you don't know what he's going to come up with.
"He's a good attacker so I've got to be alert all the time because he can offload at any time."
Tupou's six offloads were four more than the next highest from either team on Saturday night with wing partner Shaun Kenny-Dowall coming up with two of his own.
A freedom to promote the ball granted by coach Trent Robinson allowed the Roosters wingers to generate plenty of momentum for their team in the first half but Tupou admitted they pushed their luck too often in the second term.
Tupou twice came up with turnovers after making long breaks late in the second half that kept the Titans within reach and said the fatigue factor led to some poor decision-making.
"Fatigue just took over and I should have just held the ball there," Tupou said.
"I was a bit filthy on those two errors but I've just got to improve and back it up again on Thursday.
"[Robinson] does [allow us to play footy] which is good but tonight we overdid it so we've just got to go back and take the ball up and get a quick play-the-ball and get our sets started for the boys.
"The first half was pretty good, we should have just held onto the ball more in the second half."