"Initially, the surprise would likely cause long-end rates to jump higher, as heightened policy and macroeconomic uncertainty commands a higher term premium," wrote the strategists, comparing this hawkish surprise to the taper tantrum of 2013.
An early hike would perhaps also bring forward the timing of the unwinding of the Federal Reserve's balance sheet, which is chock full of long-dated Treasuries -- another potential negative for these assets.
But over the medium term, hikes coming swift and soon would help longer-dated Treasuries catch a bid for the very same reason that pushing back the timetable for liftoff would do the reverse, and perhaps prompt investors to start pricing in a reversal of these moves.
"It may even be the case that such an outcome creates risks of even lower inflation rates one year down the line," wrote the UBS team. "This could (in the extreme) trigger market expectations of cuts in 2017."