UPDATE 1-Soccer-Barca held 0-0 at home by battling Chelsea

* Barcelona held to goalless draw at Nou Camp

* Bojan misses golden chance in added time

* Marquez out for season after injury

* Pujol misses second leg through suspension (Adds details, quotes, byline)

By Iain Rogers

BARCELONA, April 28 (Reuters) - Barcelona were held to a 0-0 draw by a battling Chelsea side in the first leg of their Champions League semi-final at the Nou Camp on Tuesday.

Barca dominated possession, with Xavi and Andres Iniesta pulling the strings in midfield, but found it hard to break through the massed Chelsea defences until near the end when they squandered several chances to snatch a winner.

It was the first match is which the Primera Liga leaders had failed to score at home in any competition this season as Chelsea kept a tight rein on dangerman Lionel Messi.

Barcelona coach Pep Guardiola will have a problem picking his central defence for the second leg at Stamford Bridge next week with Rafael Marquez out for the season after a second half injury and Carles Pujol suspended following a booking.