Daniil Medvedev will have to go through two-time Miami Open champion Andy Murray to quickly reclaim the world number one ranking.
Medvedev's first stint at the top of the ATP rankings ended swiftly when he lost in the third round at the Indian Wells Masters and was displaced by Novak Djokovic.
But the Russian has the opportunity to leapfrog Djokovic once more by making the semi-finals in Miami.
Before thinking about the latter stages of the Masters 1000 tournament, however, Medvedev first must master Murray, who looked in good nick on his return to Miami.
Murray has twice won this tournament but has not played it since 2016, meaning Thursday's match against Federico Delbonis was his Hard Rock Stadium debut.
Delbonis had won the pair's only prior meeting yet was outclassed 7-6 (7-4) 6-1 after a steady first set.
Medvedev and Murray have also only met once before now, with the world number two coming out on top, but the wild card is looking forward to the challenge.
"It's a big challenge for me, a big test," Murray said. "I've got a big training block after this tournament and it'll be a really good test for where my game's at and the things I need to work on as well against him. I'm looking forward to that."
That is not the only mouthwatering second-round tie, with Nick Kyrgios through to face Andrey Rublev.
However, Stefanos Tsitsipas has a slightly more straightforward task on paper after qualifier J.J. Wolf advanced past Daniel Altmaier.