Third-quarter economic growth data might be better than expected but the fourth quarter is almost certain to be below forecasts, with November "very negative," she told the European Central Bank's post-meeting news conference.
How the virus is managed between now and the end of the year will determine what side of zero the fourth-quarter number will fall on, she added.
While stimulus measures taken by the ECB since March are helping to underpin economic activity, risks are "clearly" tilted to the downside, she said.
New staff macroeconomic projections in December will allow the ECB to make a thorough assessment of how it should recalibrate its policy response, she said.
(Reporting by Francesco Canepa; writing by John Stonestreet; Editing by Hugh Lawson)