No team with 22 points has ever yet failed to reach the last eight of the Heineken Cup as a runner-up, but Ulster will travel to Welford Road knowing they still need something to be sure of a fourth successive qualification.
"It was good to get the win but we are very disappointed not to get the bonus point. They made it very tough for us out there and we just couldn't get our attack going and we made a lot of mistakes," said Pienaar.
"We gave away too many penalties and made life difficult for ourselves. Once we got the two tries in the first half we knew the bonus point was within reach, but we failed to get it because of too many errors and penalties.
"We're happy with the win, but we've got another tough game next week. Welford Road is always a tough place to go to - Leicester are a proud team.
"But we have a good team ourselves and we will work hard this week and, hopefully, we can go down there and give them a run for their money."