Not true. Russia has recently built South Stream and North Stream pipelines, which can carry gas without transiting Urkaine.
Putin realized Ukraine will be unstable, and acted accordingly.
Russia can strangle Ukraine economically if it wants to, but it doesn’t want to, and it would hurt Russia, too.
Putin can control the pipelines in Western Ukraine by cutting off gas to Western Europe every time it gets really cold. He doesn’t need to occupy them to control the pipelines.
I was in the Czech Republic five years ago when they where scrapping and the gas flow fell to zero... all came though Ukraine via Slovakia and then on to Prague
South Stream hasn’t been completed. Gazprom is estimating the pipeline will be completed in late 2015. The main part in the depths of the Black Sea remain to be finished. I wouldn’t be surprised if the completion date isn’t a bit optimistic.
http://www.gazprom.com/about/production/projects/pipelines/south-stream/
Even after completion, together they will have far less capacity to move the product.
They are not building them to replace Ukraine pipelines, but to supplement them with more product.