"That's why Tana is the man he is, because he's all about the finer details," said Williams.
This will be his first provincial game since 2010, when he helped Canterbury defend the Ranfurly Shield against, coincidentally, Counties Manukau.
The Steelers are a long shot to crack the semifinals, so the Auckland game and Sunday's clash with Tasman could be the only matches Williams plays for the union.
He is contracted to them for 2015-16 but will most probably not get the chance to play again, with Rugby World Cup 2015 and possibly national sevens aspirations in 2016 ruling him out.
He played seven games for Canterbury in 2010 - scoring four tries - after his return from Toulon, and was fast-tracked into the All Blacks for the end-of-year tour.
When he left New Zealand rugby in August 2012 for Japan, there was little top depth at No 12. It was him and Ma'a Nonu, then daylight. Tamati Ellison, more of a natural centre, was taken on tour. Now there is Nonu, Malakai Fekitoa and Ryan Crotty, so Williams knows there is more competition.
Even at Counties Manukau, Bundee Aki and Rey Lee-Lo have hit the high notes in recent weeks, but Umaga does not see this as a headache for him.
"Bundee and Rey have played a lot of minutes this year and for them to have a bit of support when they get jaded is a positive for us ... but we'll play Sonny as we see fit," he said, adding that Williams could be an option for centre with the All Blacks next month too, as he has been in the past. Umaga has no doubt that Williams can get back to the top swiftly. He is a more mature footballer than the man who took 18 months to really get to grips with the exacting second five position, but was firing strongly in 2012 before he swapped codes again.
"He's a quick learner and is always willing to ask questions. We gave him a book with what we do and he started working on that straight away."
Williams tried to keep some rugby-specific training going, even when in league mode.
"I tried to continue the skills, so it's about bringing those back to the 15-man game. And it's the little things that count with Tana," he said.
Auckland coach Paul Feeney is expecting Williams to come off the bench and show his skills tomorrow night.
"The hype might help the team and they might feed off that and have confidence with Sonny Bill back in the fold. He was playing league a week ago, so he's obviously in good nick. His offloading will be the same and he's going to pose a huge threat. The only difference is the breakdown, where he might be a little rusty," said Feeney.
He wasn't seeking to change his side's defensive patterns too much to mark one man, as that would create holes elsewhere.
SBW in rugby 2008-13
2008-10: Toulon in French Top 14, winning 2010 Amlin Challenge Cup
2010: Wins and defends Ranfurly Shield with Canterbury
2010-12: Plays 19 tests for All Blacks and part of RWC-winning squad
2011: Crusaders in Super Rugby
2012: Chiefs in Super Rugby, winning title
2012-13: Panasonic Wild Knights in Japan Top League
