Few have given Roma a chance of progression in this year's Champions League. They are faced, in their quarterfinal, with a Barcelona side yet to lose in this season's competition. Barcelona are yet to lose domestically, too.
Barcelona, then, represent formidable opposition for Roma. The Italian club edged past Shakhtar Donetsk in the Round of 16, an Edin Dzeko goal at the Stadio Olimpico enough to see them through on away goals.
Roma might have been encouraged by Sevilla's efforts against Barcelona on Saturday. The unbeaten run was very nearly ended but for a late comeback inspired by the brilliance of Lionel Messi.
But it is the Argentine, so undeniably important for Ernesto Valverde's side, who makes the task seem all the more difficult for Roma.
Here are three key battles that could decide the outcome of the tie.