The Clark art museum in Williamstown, Massachusetts had at least four of his works in the gallery reserved for the collection's prime works on my most recent visit. One of these is his 1879 portrait of his teacher Carolus-Duran. The link to the museum's commentary on it is here.
Sargent was only about 23 years old when it was painted, and he clearly must have wanted to make a good impression. But whereas Carolus-Duran tended to include a fair amount of hard-edge detailing in portraits he painted, Sargent's treatment of him is quite soft, as the photos I took indicate. Click on images to enlarge.