Six one-day matches into his return from a nine-month lay-off after his wife Jane was diagnosed with a recurrence of cancer, McGrath has yet to find the rhythm and incisiveness that has long been his calling card.
The 36-year-old has been given a new job in Australia's two Champions Trophy matches against the West Indies and England in India, with the new ball given to the faster duo of Brett Lee and swing bowler Nathan Bracken.
Australia's plan has been to use Bracken to try to gain swing with the hard, new ball, while relying on McGrath's gnawing accuracy to take wickets and restrict the run flow while fielding restrictions apply during power plays.
But McGrath, struggling to recapture his bowling rhythm, is not relishing his new one-day role.
McGrath's first five overs against the West Indies cost just 15 runs but brought no wickets. His three-over spell at the death brought the wicket of an ailing Brian Lara and cost 27 runs.
Against England, McGrath was retired after 0-27 from his first four overs under power-play conditions, when Ashes rivals Andrew Strauss and Ian Bell attacked him.
McGrath returned to claim 2-9 from his last five overs, but his victims were wicketkeeper Chris Read and tailender James Anderson - and that did not reassure McGrath's critics.
Since last year's Ashes tour of England, McGrath has taken just 11 wickets in 13 one-dayers at 31 runs apiece and since returning from his family break last month he has just four wickets from six matches at 37.
Buchanan said he did not think McGrath would lose the use of the new ball in the Ashes but his shift to first-change in one-dayers appeared effectively permanent.
"One-day cricket and what we're doing here (in India) is slightly different to the Test match arena, because we're actually working out how to play our power plays a bit better than we have in the past," Buchanan told Australian reporters in India. His comments were reported here Thursday.
"So by utilising Glenn in that way it gives us more flexibility, but I think the Test match arena is different to that.
"I can only hand that one back to the selectors but I wouldn't have thought it would change their thinking on his role in Test cricket."
McGrath's only lengthy match before the first Test starts on Nov 23 will be a three-day game for New South Wales against England here from Nov 12.
McGrath is Test cricket's leading fast-bowling wicket taker, with 542 scalps in 119 Tests.