The negotiations for the Blues' sevens players - the now injured Ben Lam and the Ioane brothers - to return to Tietjens' squad were made before the season started, so Umaga can have no complaints, although he might have allowed himself a sense of regret when watching Akira send Rieko away for his stunning individual try from near halfway against the Sharks in the recent 23-18 victory.
Skipper James Parsons said afterwards: "A little bit of brilliance from the young fella, which he seems to do quite nicely at the moment."
After settling on a midfield of Piers Francis at second-five and Ranger at centre for the past three matches - a win over the Jaguares, narrow loss to the Chiefs (in which Rieko also scored a brilliant solo try), and win over the Sharks - Umaga must again have a re-think.
George Moala, a try-scorer shortly after coming on for the injured Ranger against the Sharks, would be a like-for-like replacement for the Northlander, with Male Sa'u also an option. Sa'u, a Japan international, hasn't been included in a Blues match day squad since the draw against the Reds in round four on March 19.
"We've got enough players who can cover for us but it's obviously not ideal to lose Rieko," Umaga said after his team's latest win.
Whatever midfield Umaga decides on, it would be better for having the 1.88m, 103kg Rieko outside it. And while his Super Rugby statistics are impressive, his sevens numbers are even better.
He played two tournaments this season - Wellington and Sydney - and New Zealand were victorious in both, with Rieko scoring 12 tries in 12 matches. That puts him fourth equal this year behind Kurt Baker (19), Sam Dickson (15), and Regan Ware (14) despite him playing far fewer matches.
Akira has scored eight tries in 12 matches.
Fitness permitting, the brothers' next sevens assignment will come in Paris on May 13, with the London tournament following on May 21.