The Nationals today acquired left-hander Tyler Robertson off waivers from the Twins. The 25-year-old is 2-2 with 6 holds and a 5.54 ERA in 42 career relief apps ('12-13). Robertson has posted a .200 BAA vs. lefthanded batters during his career. He is the son of Nationals Special Assistant to the GM Jay Robertson. Robertson will be optioned to Triple-A Syracuse.