Roberto Mancini rues Manchester City's defensive errors
Shevchenko bundled the first goal past Joe Hart from close range
Manchester City manager Roberto Mancini said conceding "two stupid goals" cost his side in their Europa League last-16 first leg defeat by Dynamo Kiev.
City were undone when unmarked Andriy Shevchenko tapped in before Oleh Gusev made it 2-0 when he eased past Micah Richards and volleyed beyond Joe Hart.
Mancini said: "We need to pay attention in the defensive phase because they were two stupid goals.
"We played a good game but made two big mistakes for the two goals."
City will face a huge task to turn the tie around on 17 March at Eastlands against a confident and well organised Dynamo side.
A disjointed City created few chances at the Valeriy Lobanovskiy Stadium, with David Silva missing the best opportunity when he failed to direct Pablo Zabaleta's scuffed cross towards goal from close range.
Mancini added: "Kiev are a good team. The right result might have been 2-1.
When you play in the Europa League, you can't concede goals like this
"We had control of the game. They played counter-attack. I'm frustrated because we conceded two goals."
City struggled to cope with the Ukrainian outfit's front quartet of Shevchenko, Andriy Yarmolenko, Artem Milevskiy and Roman Eremenko as Dynamo showed they were a step up in class from Aris Salonika, who City disposed of easily in the previous round.
"When you play in the Europa League, you can't concede goals like this," Mancini explained.
"We didn't mark well for the first goal, the second goal the same. We were four or five metres from the opponent. When you mark in the box you should be near."
City, who had won four of their last five games, will also need to rediscover their form in front of goal ahead of a crucial period as they battle for success on three fronts this season.
"I think that we had some problems and I hope that it can improve with the strikers for the return match," said Mancini.
"If the strikers improve and the defenders pay attention maybe we have a chance to go through.
"Dynamo Kiev were fresher than us tonight."
Mario Balotelli struggled to get into the game and was involved in an unusual incident when he was over a minute late coming out for the second half - which had already kicked off.
The Italian was eventually replaced by Carlos Tevez in the 57th minute after complaining of feeling unwell.
"Mario had an allergy - I don't know what. His face was swollen - I don't know why.
"He wanted to play in the second half but he had this problem 10 seconds before coming out," said Mancini.
"I came out a minute before the players and I didn't see Mario. He then said he could play but his face was swollen."
It is understood Balotelli, who arrived from Inter Milan for £24m in the summer, is allergic to certain types of grass.
City now revert to domestic issues with an FA Cup tie against Reading on Saturday. Champions League qualification, however, remains a priority and they lie third in the Premier League, seven points behind leaders Manchester United.
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