Polesitter Leclerc was passed by Max Verstappen and eventual Baku victor Sergio Perez come only lap six of 51, with the Ferrari driver opting not to fight the Red Bulls to preserve his Pirelli tyres.
The Monegasque eventually finished 21 seconds adrift of Perez but held off Aston Martin driver Alonso by 0.8s to end the two-time champion’s run of consecutive podiums at the start of the year.
Alonso reckoned Leclerc was “lucky” to hang on as late overcast conditions meant temperatures cooled to help Leclerc manage his hard tyres, with Ferrari having already shown tyre preservation struggles so far this season.
The Spaniard told Sky: “I think they got lucky. The hard tyre was less degradation than expected.
“We put the hard tyre on when the safety car came [for AlphaTauri driver Nyck de Vries clipping the Turn 5 inside wall]. It was 38 laps to the end.
“It held on quite OK and also [there] was some clouds at the end so track temperature was dropping.
“I think with the mediums, the Ferraris had massive degradation in the first stint.
“On a normal hot race, I think they will struggle a little bit more. Today was good for them but Miami [next race, humid conditions] is going to be different.”
Source: Autosport