Oita - Three head-to-heads for the Rugby World Cup quarter-final between England and Australia here on Saturday:
Farrell's return to pivot at the expense of George Ford was the major talking point in the England selection. Ford has had an outstanding World Cup so far but the beefier Farrell got the nod against Australia, with coach Eddie Jones perhaps mindful of the big Wallabies centres who will come flying down that channel.
As both England captain and first-choice goal-kicker, centre Farrell shoulders a huge burden of responsibility.
The Saracens star has not been at his absolute best with the boot at a World Cup where he has been on the receiving end of two dangerous tackles against the United States and Argentina, which some will argue is a case of incidents evening themselves out given the physically fearless Farrell's history of questionable hits.
Opponents have been able to rattle Farrell on occasion but so far this tournament his temper has remained largely in check, but there are suspicions his game management can go astray if he's put under enough pressure.
Australia's number 10 position is also not clear-cut, but Lealiifano was handed the starting role after Bernard Foley and Matt To'omua failed to convince in the key hinge position against Wales and Georgia respectively.
That cancer-survivor Lealiifano is even at a World Cup is an achievement in itself. But this week saw Lealiifanno cast doubt over his ability to start three straight games should the Wallabies go all the way to the final, after Australia coach Michael Cheika indicated the rotation at 10 had in part been a consequence of catering for his well-being.
A fine ball-player in the best Australian tradition and capable of searing breaks, Lealiifano has also showed plenty of leadership qualities as captain of the Brumbies.
It will pay to keep a close eye on the midfield where England's wrecking ball, Manu Tuilagi, will be deployed opposite fearless teenager Jordan Petaia who is playing only his third Test.
Tuilagi, finally fit after a wretched run of injuries, is destructive with the ball in hand but the athletic Petaia, 19, has already proved himself a handful, showing great footwork as he scored one try and made another in his debut against Uruguay.
Alongside them, England's Henry Slade has been thrown in at the deep as he makes his first start of the tournament facing Fiji-born Samu Kerevi, an impressive carrier.
Due to a knee injury Exeter's Slade, 26, has played just 40 minutes of Test rugby since starting in England's dramatic 38-38 Six Nations draw with Scotland at Twickenham in March.
Kerevi has been having a fine World Cup, with England defence coach John Mitchell saying he is "a strong ball carrier who they move around in structured attacks" and a "threat we have to be aware of".
Kerevi, however, has yet to go up against a defence as good as England's in Japan.
This has the look of the apprentice against the master about it, with Jones convinced his "kamikaze kids" back-row duo of Underhill and Tom Curry can be every bit as good as the dynamic Australia duo of skipper Michael Hooper and David Pocock.
Jones said he gave his pair their nickname because they "hit everything that moves".
Hooper, however, has long been acknowledged as one if the world's best operators at the breakdown and with French referee Jerome Garces - not as strict as some officials in this area - the experienced Wallaby star may be given the leeway to cause England plenty of damage this weekend.
15 Elliot Daly, 14 Anthony Watson, 13 Henry Slade, 12 Manu Tuilagi, 11 Jonny May, 10 Owen Farrell (captain), 9 Ben Youngs, 8 Billy Vunipola, 7 Sam Underhill, 6 Tom Curry, 5 Courtney Lawes, 4 Maro Itoje, 3 Kyle Sinckler, 2 Jamie George, 1 Mako Vunipola
Substitutes: 16 Luke Cowan-Dickie, 17 Joe Marler, 18 Dan Cole, 19 George Kruis, 20 Lewis Ludlam, 21 Willi Heinz, 22 George Ford, 23 Jonathan Joseph
15 Kurtley Beale; 14 Reece Hodge, 13 Jordan Petaia, 12 Samu Kerevi, 11 Marika Koroibete; 10 Christian Lealiifano, 9 Will Genia; 8 Isi Naisarani, 7 Michael Hooper (capt), 6 David Pocock; 5 Rory Arnold, 4 Izack Rodda; 3 Allan Alaalatoa, 2 Tolu Latu, 1 Scott Sio
Substitutes: 16 Jordan Uelese, 17 James Slipper, 18 Taniela Tupou, 19 Adam Coleman, 20 Lukhan Salakaia-Loto, 21 Nic White, 22 Matt To'omua, 23 James O'Connor