Sordo began the afternoon loop 0.7 seconds behind Toyota’s Ott Tanak in third, and duly beat his rival by that same 0.7s to draw level with Tanak heading into stage seven.
Stage seven Castelsardo stage was then cancelled as a spectator required medical attention, but not before the leading three drivers on the road - Tanak, Thierry Neuville and Elfyn Evans - all managed to complete it.
This has left rally organisers with a decision as to what nominal time to give the remainder of the field, and forced Tanak, Neuville and Evans to complete the loop with tyres that were in a worse condition than the rest.
Sordo went 4.7s faster than Tanak on the next competitive test and 6.5s quicker on the final stage, which should be enough to see him lead Tanak and M-Sport’s Teemu Suninen overnight.
Jari-Matti Latvala had led the rally heading into the afternoon, but his challenge ended on the first test.
He clipped the inside of a tight hairpin on Tula, rolling his Yaris WRC onto its side. He and co-driver Miikka Anttila managed to overturn the Toyota but limped to the end of the stage with a broken windscreen, losing well over eight minutes.
Latvala responded with a fourth fastest time despite no windscreen on the following test, only for his Yaris to veer left and off the road on Monte Baranta that concluded the afternoon.
M-Sport driver Evans lost ground when he nudged a bank on stage eight Tergu-Osilo and shot into a hedge after struggling to stop his Fiesta. He managed to reverse out, but dropped 9.5s to Tanak after closing to within 1.2s on the previous stage.
Andreas Mikkelsen lamented his incorrect tyre choice in the morning because “he could have been right up there” as he fought to keep Kris Meeke behind him.
He blasted to a stage win on Monte Baranta that could potentially elevate him past Evans into fourth.
Meeke had a quiet afternoon, keeping his Toyota out of trouble to hold sixth.
Hyundai’s Neuville endured a ragged afternoon but survived to lie seventh, albeit 46.5s behind championship rival Tanak.
Neuville and co-driver Nicolas Gilsoul had a “misunderstanding with a pace note” towards the end of Tula, the pair damaging the radiator on their Hyundai as they lost the rear and nudged a bank.
Two stages later and Neuville evaded further disaster, starting the test on tyres he described as “slicks”.
He suffered a big slide into a right hander early on, narrowly avoiding a hole on the inside bank. He then overshot a junction later on the stage, completing Tergu-Osilo with no front bumper.
Esapekka Lappi set some encouraging pace across the afternoon, but the Citroen driver finds himself over a minute behind the lead in eighth after he knocked a tyre off the rim in the morning.