Platini saw the FIFA presidency as his destiny, but the UEFA leader was prevented from running in February's election when a payment of 2 million Swiss francs (USD 2 million) from the global governing body was exposed.
Instead, Infantino was plucked from the relative of obscurity of the UEFA general secretary job to become Europe's candidate to succeed Sepp Blatter.
Infantino received the news that the Court of Arbitration for Sport had reduced Platini's ban to four years while in Mexico City preparing for his first congress as FIFA president.
The CAS panel ruling clears a potential barrier to Infantino seeking a second term leading FIFA. The election will be in approximately May 2019, and Platini will remain banned until late 2019.
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FIFA's appeal panel cut two years off their sanctions in February as reward for their long service to the sport.
Both men are appealing to CAS, but Platini's case was heard first, and another two years were slashed from his ban.
CAS said it was "not convinced by the legitimacy" of Platini being paid 2 million Swiss francs by FIFA in 2011, nine years after his work as a Blatter adviser ended when he joined the executive committee.
Asked if FIFA would now seek to reclaim the cash, Infantino said: "Now is not a moment to speculate about these things."