Sunderland scored his first stage win of the 2021 Dakar on the shortened 464km Al Ula-Yanbu stage, more than halving the 10-minute deficit he faced to Honda man Benavides.
The British rider, who is chasing a second Dakar win, took control at the 215km mark and from there extended an advantage of 2m40s over Husqvarna's Pablo Quintanilla.
Benavides was third-fastest, dropping 6m24s on Sunderland to give himself a buffer of 4m12s heading into Friday's decisive stage.
Ricky Brabec's hopes of defending his 2020 title look to be fading fast after the American rider conceded six minutes to Benavides and nearly 13 to Sunderland.
The Honda rider opened the road following his victory on Wednesday, but was quickly caught by Benavides as the two rode in tandem for the majority of the stage.
Brabec goes into the final stage of the rally 7m13s down on Benavides.
Joan Barreda meanwhile has officially joined Honda teammate Jose Ignacio Cornejo on the retirements list after running out of fuel on the stage. The Spaniard, the winner of three stages on this year's event, has been airlifted to the Yanbu bivouac.
KTM rookie Daniel Sanders was fourth on the stage, and with Barreda and Cornejo both out, he now finds himself in the same position overall, 33 minutes off the lead.
Privateer Skyler Howes (KTM) has just 19 seconds in hand over Sherco rider Lorenzo Santolino in the fight for fifth place, while Quintanilla is up to seventh.
Adrian van Beveren, the only Yamaha factory rider still in the event, climbs to eighth.
Standings after Stage 11 (Top 10):
Adrien van Beveren