LONDON - Chelsea manager Antonio Conte rued one costly mistake as Lionel Messi gave Barcelona the upper hand from the first leg of their Champions League last-16 tie by salvaging a 1-1 draw at Stamford Bridge.

Messi struck for the first time in nine games against Chelsea 15 minutes from the end, as Andres Iniesta punished the English champions once more when he intercepted Andreas Christensen's slack pass across his own box to tee up the five-time World Player of the Year. Willian's fine strike just after the hour mark had put Chelsea in command after he had hit both posts in the first half.

Chelsea must now score when they travel to the Camp Nou on March 14 to have any chance of making the last eight. Nine years on from combining for a stoppage-time equaliser in a highly controversial semi-final at Stamford Bridge to send Barca to the final, Iniesta and Messi swapped roles as this time the Spaniard provided the pass and Messi the finish. Conte sprang a surprise before kick-off by leaving out both Olivier Giroud and Alvaro Morata with Eden Hazard instead operating in the middle of a front three. And it was Hazard who sent the first warning that Barca were in for an uncomfortable evening when he fired just over from 20 yards five minutes in.

Chelsea constantly tried to surround Messi with three or four blue shirts to limit the Argentine's threat, but he dug out a cross to the far post where an unmarked Paulinho headed Barca's best chance of the first-half wide. Barca then went on to dominate possession, but the visitors lacked penetration and were lucky to go in level at half-time.

Willian scored twice from outside the box against Hull City in the FA Cup on Friday, and was inches away from another long-range stunner when he curled onto the post from 25 yards with Marc-Andre ter Stegen beaten in the Barca goal. Barca had kept six clean sheets in their previous seven Champions League games, but once again had good luck rather than good defending to thank four minutes before the break when Willian hooked another effort from outside the box off the woodwork.

MUELLER SHINES AS BAYERN THRASH 10-MAN BESIKTAS:  Thomas Mueller and Robert Lewandowski netted twice as Bayern Munich thrashed 10-man Besiktas 5-0 on Tuesday in the first leg of their Champions League last 16 tie.

Disaster struck for Besiktas after just 16 minutes at Munich's Allianz Arena when Domagoj Vida was sent off for bringing down Lewandowski as the Poland striker was through on goal. Besiktas held firm until just before half-time when Bayern captain Mueller scored from close range. The floodgates opened after the break at Munich's Allianz Arena as Kingsley Coman struck before Mueller poached his second. Bayern claimed their fourth on 79 minutes when Lewandowski pounced on a rebound after defender Mats Hummels's long-range shot was parried. Mueller then weighed in with an assist to set up Lewandowski for the fifth just before the final whistle.

Besiktas, making their debut in the knock-out stages of the Champions League, face a near impossible task in the return leg in Istanbul on March 14 if they are to prolong their European adventure. Bayern made a bright start when Coman's curling shot forced Besiktas goalkeeper Fabri into a save on nine minutes, Joshua Kimmich's free-kick was then headed wide by Arturo Vidal.

But Besiktas were the architects of their own downfall as a poor pass from skipper Atiba Hutchinson was snapped up by Lewandowski, who was sent tumbling by last man Vida as he closed in on goal. Despite the dismissal of the Croatia defender, Bayern initially struggled to make the advantage count as the Besiktas defence, marshalled by Portugal veteran centre-back Pepe, refused to buckle. The Turkish champions created chances of their own as winger Ricardo Quaresma beat Bayern centre-back Hummels before firing wide, while Pepe shot over the bar. But Bayern broke the deadlock when Coman whipped in a cross and David Alaba flicked the ball to Mueller, who tapped the ball through Fabri's legs on 43 minutes.

Colombia playmaker James Rodriguez went off with a calf injury just after the goal, replaced by veteran winger Arjen Robben, a surprise exclusion from the starting side, in a move that pushed Mueller more central to accommodate the Dutchman. Bayern maintained the pressure following the restart as Lewandowski hit the post with a free-kick four minutes into the second half.

The Poland forward turned provider for Coman's goal, passing back inside after being put in behind the defence by Mueller. With the Besiktas defence worrying about Mueller and Vidal, Coman steamed into the area unmarked to slam home Bayern's second goal on 52 minutes. As Bayern continued to pepper the Besiktas goal, visiting coach Senol Gunes sacrificed striker Vagner Love for defender Dusko Tosic to try and limit the damage.

It had little effect though as Bayern grabbed their third when Kimmich's cross was met by Mueller at the near post on 66 minutes. A speculative Hummels shot was then kept out well by Fabri, but Lewandowski was on hand to tuck away his 28th goal of the season in all competitions on 79 minutes. Mueller and Lewandowski combined for Bayern's fifth goal when the Germany forward squared for his Polish team-mate to cap the rout two minutes from time.