Chelsea striker Didier Drogba is likely to miss the start of the season after undergoing a groin operation.The club described the procedure performed on the Ivory Coast international as "minimally invasive".And it is expected that Drogba, 32, will return to full training in about three weeks.That estimate would, however, put him out of the Charity Shield match against Manchester United on 8 August and the start of the Premier League campaign.A short statement on Chelsea's official website said he had been troubled by a groin injury for part of last season and the decision to have the operation on Friday was intended to "optimise his rehabilitation".Drogba has been a prolific scorer for Chelsea since joining them from French club Marseille in July 2004 for a reported fee of £24m and was on target 37 times during the 2009-10 season to help the team to a first Premier League and FA Cup Double.He then went to the World Cup with the Ivory Coast squad and despite fracturing his right arm in a pre-tournament warm-up game, played in all three group matches wearing a protective cast.Drogba scored in the 3-1 defeat by Brazil as the Elephants failed to progress to the last 16.Chelsea have a serious of injury concerns ahead of the new Premier League campaign, which they will begin with a home match against newly promoted West Brom on 14 August.New signing Yossi Benayoun also has a groin problem, first-choice goalkeeper Petr Cech is expected to be out for about a month because of a calf injury and defender Alex hurt his thigh in training.Credit: BBC