Smith replaced Lardarius Webb after he went down last month with a knee ligament tear that ended his season. Receiver Torrey Smith played through the injury a year ago, but playing cornerback makes playing through such an injury almost impossible.
"Torrey had a similar deal last year and was able to play through it. Jimmy was not, because it was just a little different position, and the details were a little different as far as the injury in there,” Harbaugh said. "He went ahead and got it corrected."
Smith had surgery Thursday in Philadelphia. Corey Graham, who was used primarily in nickel packages and special teams, will start for the second game in a row in his place.
Graham took the field vs. the Oakland Raiders last week, a 55-20 win for Baltimore. Smith was expected to play but was a late scratch because of the discomfort. The Ravens acquired veteran free agent Chris Johnson earlier this week. They also could activate rookie Asa Jackson for the first time this season.
Harbaugh is optimistic he’ll get Smith back.
"It looks like, by all accounts, it went really, really well, and the timeframe – it’s hard to say exactly what it is – but by the end of the season there is a really, really good chance he will be back playing," he said.