* Substitute Messi scores in 2-2 draw
* Second-placed Real beat Atletico 2-1 (Adds late result, Real quotes)
By Iain Rogers
MADRID, April 27 (Reuters) - Barcelona must wait at least another week to wrap up the La Liga title after conceding a late goal to draw 2-2 at Athletic Bilbao on Saturday before second-placed Real Madrid won 2-1 at city rivals Atletico.
Victory for Barca at the San Mames and defeat for Real in the Madrid derby at the Calderon would have given the leaders an unassailable 16-point advantage with five matches left.
Real's comeback win meant Barca's lead was cut to 11 points and they also pulled six points clear of Atletico, who are third and almost assured of a Champions League place for next season.
Barca must wait until after their likely elimination from Europe's elite club competition at home to Bayern Munich on Wednesday for another chance to secure a fourth Spanish crown in five years.
"We are leaving with a bitter taste in our mouths but feeling satisfied with the job done," Barca forward Alexis Sanchez, who netted his side's second goal, told reporters.
With an eye on the Champions League semi-final second leg, when Barca need to overturn a 4-0 deficit against the Germans, coach Tito Vilanova initially left league top scorer Lionel Messi and playmaker Andres Iniesta on the bench.
Bilbao, without a home win in six La Liga games against Barca, took a surprise 27th-minute lead when Markel Susaeta finished from close range from an Aritz Aduriz cross.
Barca huffed and puffed in search of an equaliser but were fortunate not to fall 2-0 behind when Susaeta struck a free kick against the crossbar 10 minutes into the second half.
Only when Argentina forward Messi, who had missed the last three league games with a hamstring strain, came off the bench on the hour did Barca find their cutting edge.
The World Player of the Year brilliantly weaved his way through a crowd of defenders to equalise in the 67th minute and Alexis, who had earlier struck a post, made it 2-1 two minutes later from a Messi assist.
Messi's goal, his 44th in 33 league matches this season, set another record as it took his tally away from home to 24, one more than Real Madrid forward Cristiano Ronaldo got last term.
The Argentine has also scored at least one goal in his last 20 league appearances while Barca equalled their La Liga record by scoring for the 26th consecutive away match.
They looked to have another three points safely in the bag before Bilbao midfielder Ander Herrera rifled a low shot into the corner of the net after 90 minutes to send the home fans into raptures on a wet and chilly night in the Basque Country.
"The Athletic stadium is a very difficult place to play and you saw that as we had the match won," Barca assistant coach Jordi Roura told a news conference.
"We are closing in on our goal bit by bit."
Real Madrid, 4-1 down to Borussia Dortmund after Wednesday's semi-final first leg, also face Champions League elimination but coach Jose Mourinho fielded a second-string side at Atletico.
He was also missing Portuguese compatriot Ronaldo, Real's top league scorer with 31 goals, who damaged a thigh muscle at Dortmund.
Atletico, who began the game three points behind Real in third spot and seeking a first win in 22 meetings with their city rivals, took the lead in the fourth minute when Colombia striker Radamel Falcao nodded his 26th league goal this season.
Real were level nine minutes later when Angel Di Maria's inswinging free kick took a slight deflection off defender Juanfran and flew past keeper Thibaut Courtois into the net.
After Real repelled some intense Atletico pressure, Di Maria struck a 63rd-minute winner after running on to Karim Benzema's pass and firing a low shot past Courtois into the far corner.
It was a rare moment of quality in a scrappy game littered with play acting, fouls and yellow cards that was a poor advert for next month's King's Cup final when the two teams will meet at the Bernabeu.
"We haven't given up on the league," Di Maria said in an interview with Spanish broadcaster Gol Television.
"The coach picked the players he thought were needed and we did things well," he added. "We got a good result and we are still in the fight."
Barca host Real Betis next weekend while Real Madrid take on Real Valladolid.
Also on Saturday, Celta Vigo boosted their chances of avoiding the drop when they won 1-0 at Levante.
Real Zaragoza came out on top in a relegation battle with Real Mallorca when Ruben Rochina's 88th-minute strike secured a 3-2 home win to put them on 30 points with Deportivo, who visit Betis on Monday, and Celta who are both in the safety zone. (Editing by Tony Jimenez and Ken Ferris)