Atletico Madrid and Barcelona showed the battle for the La Liga title would be a long, drawn-out affair after the co-leaders drew 0-0 on Saturday.
Both clubs finished the first half of the season tied on 50 points after an exciting, back-and-forth showdown at Vicente Calderon Stadium yielded no winner.
Barcelona were troubled by Atletico striker Diego Costa throughout, while second-half substitute Lionel Messi enjoyed the visitors' best chances as the Barcelona forward headed wide before forcing goalkeeper Thibaut Courtois into a clutch stop in the 81st minute.
Neymar also came on in the second half for Barcelona but the Brazil striker made little impact as the teams played out their third straight draw following the summer Spanish Super Cup series.
Atletico started more brightly behind Diego Costa as the Brazilian-born striker's short cross along the goal-line was headed just over for the game's opening chance four minutes in.
The physical Diego Costa forced goalkeeper Victor Valdes into a save before awkward positioning kept him scoring from a headed-on corner in the 28th minute.
Barcelona braved Atletico's early surge and their choking pressure up the field with its passing game, with Pedro Rodriguez heading over goal in the 33rd minute before Courtois saved Gerard Pique's long, low shot.
Messi replaced Andres Iniesta to start the second half but it was Diego Costa who continued to prowl Barcelona's goal only to shoot wide in the 59th minute.
Messi perhaps showed some rust from a two-month injury layoff when he headed Jordi Alba's cross wide from the penalty spot at the other end.
Atletico looked set to break through in the 79th minute but Arda Turan volleyed a looping ball straight at Valdes, moments before Courtois denied Messi's hard-taken shot from the left.
Athletic Bilbao maintained their grip on fourth place by demolishing Almeria 6-1.
Mikel Rico, Ander Herrera, and Aymeric Laporte all scored first half-goals before Helder Barbosa pulled one back for the visitors in the 34th minute.
But Bilbao continued to dominate in the second half at their new San Mames Stadium as Aritz Aduritz restored the three-goal cushion before Ibai Gomez scored a brace, including a late penalty.
Athletic enjoy a four-point cushion in fourth place at the halfway point of the season, while Almeria sit three points above the drop zone.
Celta Vigo rallied for a 2-1 win that left Valencia mid-table with 23 points -- provisionally six behind eighth-place Sevilla.
Celta's Charles capped an entertaining contest in the 78th minute with his second goal as the Brazilian striker shook off his marker to unleash a rising shot from outside the area that ended in the top corner.
Charles had cancelled out Daniel Parejo's first-half opener after the restart, and Valencia watched Sofiane Feghouli's header come off the post on the stroke of stoppage time.
Celta moved three points clear of the relegation zone with the victory.
Daniel Carrico scored in the last minute as Sevilla rallied to draw 1-1 at Elche.
Cristian Herrera's 82nd-minute effort had looked set to earn the struggling hosts a crucial three points, but their hopes of moving four points clear of the bottom three were dashed.
Instead they gained a two-point cushion over the drop zone, the draw no more than they deserved from a match in which they frustrated European hopefuls Sevilla for long periods.