* Barca dominate but fail to breach Atletico defence
* Pair lead standings on 50 points at season midpoint
* Real can close to within three with win at Espanyol (updates with late game in last para)
By Iain Rogers
MADRID, Jan 11 (Reuters) - Title rivals Barcelona and Atletico Madrid stayed locked together at the top of La Liga after they played out an intense 0-0 draw with few genuine chances at the Calderon on Saturday.
Not even the introduction of Barca's fit-again World Player of the Year Lionel Messi at halftime or Brazil forward Neymar with just over 20 minutes left could break the deadlock and both teams have 50 points at the halfway stage of the campaign.
"They are a very, very compact side, one of the best teams in Europe and physically very strong," Barcelona captain Xavi said in an interview with Spanish TV broadcaster Canal Plus.
"We had our chances but it was an extremely intense match and in the end a draw," added the Spain playmaker.
"Normally in the final 15, 20 minutes against them is when we finish stronger and have chances to score but it was a finely-balanced game and Atletico are a great team.
"They have a different style to us but defensively they are excellent and they allow you very little space."
The result was good news for third-placed Real Madrid, who can close to within three points of the joint leaders - Barca are top on goal difference - with a win at Espanyol, the only team to beat Atletico this season, on Sunday (1800 GMT).
Real lost 1-0 at home to Atletico at the end of September and went down 2-1 at Barca in October's "Clasico" but have not been beaten since then and are likely to be challenging for the title when the league reaches its climax in May.
Saturday's closely-fought encounter was similar to the home and away clashes between Barcelona and Atletico in the season-opening Spanish Super Cup, when they drew 1-1 at the Calderon in the first leg before the return at the Nou Camp ended 0-0.
Atletico, who had won all nine of their home league matches this season before the visit of the champions, started stronger and their Turkey midfielder Arda Turan and Spain forward Diego Costa created some early danger for the visiting defence.
However, Barca gradually began to exert their customary control, with Xavi and Sergio Busquets pulling the strings in the middle, and threatened the home goal in the 33rd minute when Pedro headed Andres Iniesta's cross over the bar.
Iniesta took a knock to the knee in the first half and was taken off as a precaution at the break.
The Spain playmaker made way for Messi, who on Wednesday played for the first time in almost two months since recovering from a thigh strain and scored twice in a 4-0 King's Cup last 16, first leg win at home to Getafe.
The Argentina international drew a fine save from Atletico goalkeeper Thibaut Courtois with a fizzing low shot in the 81st minute but otherwise made little impact against a typically resolute home defence.
The vociferous Atletico fans, whose team have not won the league since 1996, seemed satisfied with the draw against their vastly wealthier rivals after the whistle, chanting "Atleti! Atleti" as the players swapped shirts and trooped off the pitch.
"We were expecting an intense game against one of the best teams in the league and we are pleased with the result," Atletico captain Gabi told Canal Plus.
"We will continue to take each game at a time and I think the team has performed extraordinarily well in the first half of the season," he added.
"It will be tough to repeat that in the second half but hopefully we can manage it."
Celta Vigo inflicted a first defeat on Valencia's new coach Juan Antonio Pizzi with a 2-1 home victory, while fourth-placed Athletic Bilbao moved to 36 points, four clear of Real Sociedad in fifth, with a 6-1 win over promoted Almeria at the San Mames.
In the late game, Sevilla snatched a 1-1 draw at lowly Elche with an 89th minute equaliser by Daniel Carrico and stay seventh on 30 points, one behind Villarreal who host Sociedad on Monday. (Editing by Ken Ferris)