It should be recalled that where, as in the present case, a contract is awarded after a call for tender, the decision on whom to award the contract to is based on the offers made by bidders. In an area like the one at issue in the present case, which concerns the provision of services by experts, the quality of the experts put forward by a bidder is likely to play a significant role when it comes to the decision on awarding the contract. Allowing a contractor to proceed to the replacement of one of the experts initially put forward by it without good reason would therefore entail the risk of changing factors that may have been important or even decisive for the award of the contract.