The Vatican on Thursday opened the most solemn period of Holy Week with a recovering Pope Francis largely on the sidelines, as cardinals were designated to take his place presiding over the most important liturgical services leading up to Easter.

Pope Francis, still recovering from double pneumonia, did not attend an annual procession on Friday at Rome's Colosseum with thousands of Catholic faithful for the third year in a row.

Holy Week is a time when the pope would be expected to be front and center of events. But as Francis continues to recover from double pneumonia, observers are on the lookout for surprise appearances.