Charles Leclerc is set to drive the SF90 on Tuesday morning before handing over to teammate Sebastian Vettel for the afternoon. Wednesday sees Vettel begin the day before handing over to his Monegasque teammate after lunch.
Though some doubt the wisdom in not allowing drivers a full session in which to become fully acclimatised with the car, in addition to the extra work involved in adapting the car over the lunch break, it's a tactic which doesn't appear to have done Mercedes any harm over the years.
The German team first began alternating its drivers in this way part-way into 2014 pre-season test, while from 2017 it has become its regular practice.
Having pretty much dominated the first week of testing, in terms of pace and mileage, the second week sees the pressure ramped up and Ferrari clearly feels that this is one area where it can learn from its rival.
Over the course of the opening test, the Mercedes duo of Lewis Hamilton and Valtteri Bottas completed 1,764 miles (2,839 kms) of trouble-free running, while the Maranello pair completed 1,729 miles (2,783), Vettel completing 876 miles (1,410 kms) and Leclerc 853 (1,373 kms).