Manage with contracts to improve your project success. Define scope and roles clearly. Putting a lot of the project work out to contract is one way, with the benefit of being able to control the schedule and cost by applying contract terms. Or contract internally.
Projects often fail because the project team members are not clear on their roles and responsibilities. Make sure your project team members know what they are supposed to do with defined roles, clear role descriptions and briefs of what they should be doing.