Spain has World Cup qualification in their own hands going into the final round of games after securing an important 1-0 in Greece.
Luis Enrique's side took advantage of a surprise slip from previous Group B leaders Sweden, who lost 2-0 in Georgia earlier on Thursday, to leapfrog them into first place.
Pablo Sarabia stepped up with the all-important penalty on the 26th minute. La Roja can now book their place at Qatar 2022 if they can avoid defeat to Sweden on Sunday in Seville.
Greece thought they had taken the lead on 21 minutes as Giorgos Masouras finished well from a Thanasis Androutsos through ball, but the Olympiakos forward was just offside.
Just three minutes later, Spain won a penalty after Inigo Martinez was felled in the box by Dimitris Giannoulis following a corner, and Sarabia sent Odisseas Vlachodimos the wrong way to put La Roja ahead.