MLS Conference semifinal preview: Cascadia and I-95 rivalries headline final eight

The New York Red Bulls face off against familiar foe D.C. United while Pacific Northwest foes Portland Timbers and Vancouver Whitecaps collide.

After a dramatic knockout round for the ages, the 2015 MLS playoffs have already set the bar high for excitement and drama. As tough as it will be to keep up the crazy level set up by the first round matches, the conference semifinals are shaping up to offer plenty of drama of their own.

Each conference features one rivalry clash and one meeting of in-form sides, with all four matches having plenty of story lines. The New York Red Bulls and D.C. United have made playoff meetings a regular part of MLS tradition, though there are reversed roles this…