Coventry - Billy Vunipola said being confronted by a spectator after Saracens' European Champions Cup semi-final win over Munster was "quite scary".
The England No 8 was booed throughout the match by Munster fans, who vastly outnumbered Saracens supporters in a crowd of some 16 000 at Coventry's Ricoh Arena on Saturday.
But that did not stop him producing a man-of-the-match display that saw the back-row forward score Saracens' second try in a 32-16 win.
A picture of the incident showed Vunipola being approached by a man wearing a Munster shirt who gestured at the him with his fingers as the Saracens star joined team-mates on a lap of honour.
The jeers at Vunipola came just days after he was warned by his club and the Rugby Football Union for publishing a controversial statement on social media.
Vunipola said on Instagram and he also liked a post from Australia's Israel Folau that stated for homosexuals.
In a post-match interview with BBC Radio, Vunipola said the approach by the fan had been "quite scary".
Vunipola added, however, he had been prepared for the boos.
"People say I put my foot in it so I have to deal with it," he explained.
"It's not something I'm afraid of. I probably have to expect that it's going to keep happening. It was quite a motivating factor that people were booing me. I wanted to back up my words and show my team-mates that I did not mean to distract them."
The fan who confronted Vunipola was soon led away by stewards.
Reflecting on the fall-out from expressing his religious views, Vunipola admitted Saturday: "It was probably insensitive, but also something I strongly believe in. I'll probably not be as honest as I have been about things that probably hurt a lot of people. I know that now."