So you've figured out when your goal events will be, and you discover that you don't have the 28 weeks required to complete the entire Base/Build/Specialty progression. While not ideal, you don't need to worry. There are still big gains to be had.
When put in this situation, many athletes decide to shave off weeks by cutting out the Base Phase, but in most situations, this is not the best option. To find out if your particular situation is an exception, check out the "Can I Skip Base" section of the Principals of Base Training article.
Base training is immensely important because each phase of training builds upon the last. If your Base is weak, then your Build training will not be as effective as it should be. If your Base and Build phases were not effective, then your Specialty Phase will not be effective either. To learn more about why Base Training is critical to your training progression, check out the "Principals" section of the Principals of Base Training article.
Now onto what you should do. In almost all cases, it is best to start with Base and complete as much of the plan as you possibly can. Whether that means you only get through Base, or halfway through Build, or halfway through Specialty, it is important that you build from the ground up. A house built upon a weak foundation cannot stand. This is how I like to think about it:
This phase is where you build the foundation for your home. You run the pipes, the electrical and you pour the concrete upon which you will build your house.
This phase is where your house is built. At the end, you have a standing, but unfinished home.
This phase is where you go through and complete the finishing touches. Roofing, carpets, paint, and tile all happen in this phase.
Looking at training through this analogy helps us understand why things are done in their specific order. We could certainly build the house with no foundation, however, there would be fundamental flaws like no electrical, no sewer, and the house could collapse under pressure. Similarly, there is no point in bringing carpet into a home that hasn't been constructed yet. Without the home to put them in, carpet, tile, and paint have little value. Everything must be done in its specific order in order to create a quality end result.
Two weeks before your event:
This is where things deviate slightly from the "complete as much as you can" approach. In most cases, in the final two weeks before your event, you are going to want to complete a taper. A taper is when you decrease the overall volume of your training while keeping the intensity present. This intensity allows you to keep your legs' "snap", and maintain familiarity with the physical and mental demands of high-intensity riding while eliminating fatigue through the reduced volume to keep you feeling fresh for race day. To choose the appropriate taper, you will simply select the Specialty Phase that best matches your target event. You will then complete only Weeks 7 and 8 of that plan in the two weeks leading up to your event. It’s important to note that low-volume riders often don’t need to taper at all, and mid-volume riders often benefit from a single-week taper. Let your prior training volume and fatigue be your guide when deciding how long you’ll taper.
Takeaway: If you're going to have to skip phases, you may be tempted to skip Base, however, this is seldom the best option. Start from the bottom and work your fitness up as far as you can.