The season is only one race old but warnings are already flashing that Mercedes could dominate this year like few before it after world champion Lewis Hamilton led an untroubled one-two finish in Australia.
McLaren's Jenson Button is convinced the celebrated marque can figure in 2015, but they have a long road ahead after the Briton trailed home 11th and last at the season-opener in Melbourne.
Alonso's second stint at McLaren will get off to a delayed start at the Sepang circuit, subject to final medical clearance on Thursday, with questions still hovering about his crash in testing on February 22.
The MP4-30 of Alonso, who suffered temporary memory loss in the accident, will be fitted with an extra sensor after he recalled "heavy steering" before the crash on an innocuous stretch of Barcelona's Circuit de Catalunya, said McLaren.
Although McLaren's expectations will be modest, Alonso was bullish as he tweeted about the three wins at Sepang which have made him one of the race's most successful drivers.
"Three victories with three teams," the two-time world champion posted in Spanish, highlighting his 2005, 2007 and 2012 triumphs for Renault, McLaren and Ferrari respectively.
World body International Automobile Federation’s medical staff will be busy on Thursday with Williams' Valtteri Bottas also seeking clearance from a back problem which ruled him out in Australia.
And Manor are expected to make a delayed debut after the new team, built from the detritus of failed outfit Marussia, were unable even to leave their garage in Australia.
Manor's woes, plus Bottas's injury, Alonso's absence on medical advice and mechanical problems for McLaren and Red Bull combined to leave just 15 cars on the Melbourne grid, the lowest number at a season-opener since 1963.
With Mercedes' dominance prompting Red Bull to hint at quitting Formula One, it was far from a smooth start even for a sport which is well used to crisis and controversy.
Inherent financial difficulties were underlined when Germany later announced it was unable to host a grand prix this year, ending a run of 54 consecutive races.
On the more positive side, Brazil's Felipe Nasr, 22, shrugged off legal challenges over Sauber's driver line-up to finish fifth in Australia on his Formula One debut.
And Max Verstappen, 17, will also hope to build on an encouraging start when the sport's youngest ever driver drove solidly before he suffered a mechanical failure.
But calls for change will only grow louder if Mercedes repeat their crushing performance in Melbourne, when Hamilton and teammate Nico Rosberg outstripped their rivals by more than 30 seconds.
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