Oxford University were sunk by a last-minute penalty as they went down 19-17 to the Portugal national side.
And to make matters worse for the Dark Blues, Danny Palm was taken to hospital with a suspected fractured cheekbone as tempers flared in the latter stages.
Oxford conceded an early try, conversion and penalty to trail 10-0.
It took them 30 minutes to get off the mark, a try from centre Sam Humphrey-Baker and conversion by Joe Roff reducing the deficit.
However, two penalties saw Portugal go 16-7 ahead.
From a quick turnover in the second half, Tom Tombleson scampered over in the corner.
Two minutes later, Tombleson ran from the halfway, beating several defenders before sliding into the corner and giving the Blues a one-point lead.
With tension running high in the final ten minutes, the Portugese openside flanker was sin-binned after a challenge that saw Palm carried off.
But with Oxford repeatedly penalised in the final minutes, Portugal slotted a crucial kick to claim a narrow win.
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