 Emperor Yang was impressed with Yu's talent and began to promote him, particularly after Liu Guyan (柳顧言), the head of the Palace Library, endorsed Yu, and Yu was promoted to be the deputy head of the legislative bureau.His mother soon died, however, and he left imperial service to serve a mourning period, although Emperor Yang soon recalled him to governmental service.Emperor Yang made him, along with Niu Hong (牛弘), Su Wei, Yuwen Shu, Zhang Jin (張瑾), Pei Yun (裴蘊), and Pei Ju in charge of selecting and promoting officials, and they were known as the "seven nobles of officialdom."