Fitting six pace bowlers into a likely five vacancies is one of the toughest selection conundrums in New Zealand ODI history.
Trent Boult and Tim Southee appear certainties. After that, a verdict is required on whether to take Mills' experience, Matt Henry's subtlety, Mitchell McClenaghan's aggression or Adam Milne's pace. Hamish Bennett and Doug Bracewell remain on standby for a crisis.
Henry's phenomenal series against Pakistan, when he took 13 wickets at 16.30, has since been tempered by two wickets at 105 and an economy rate of 8.40 in three Ford Trophy matches for Canterbury. In comparison, Auckland's Mitchell McClenaghan has 11 wickets at 9.36 while conceding just 3.91 runs an over and Central Districts' Adam Milne has five wickets at 23.20 and an economy rate of 7.10.
Mills' 237 ODI wickets have come at a mere 26.94 and handy modern-day economy rate of 4.73 in 167 matches. He's made 1017 runs at 15.64 and a strike rate of 80, including two half-centuries.
Such a pedigree heading into a World Cup is precious but last year his seven wickets came at 44.14, so he needs to find form. It would be cruel if Mills misses out at home in a career of service which saw him ranked as the world's No 1 ODI bowler in 2009.
Regardless, Mills' injury came at an appalling time as he contemplates what would likely be a final World Cup.
In an almost 14-year international career, Mills has played just four World Cup matches. He bowled six overs in 2003 and played Zimbabwe, Pakistan and Canada in 2011 before straining his left quadricep. A knee injury curtailed his chances of attending in 2007.