Milan centre-back Mattia Caldara has undergone surgery on the knee injury he picked up in training in midweek, with the 25-year-old expected to spend up to six months on the sidelines as a result.
The Italian international joined the Rossoneri from Juventus for €35m last summer, but is yet to make a league appearance following a string of fitness issues. His early San Siro career was hampered by minor problems before a ruptured achilles tendon kept him out for four months, the defender only returning to the side last week.
Caldara - who was unveiled as a Milan player alongside Gonzalo Higuain in August - made his comeback during the Coppa Italia semi final defeat to Lazio last week, putting in a strong performance despite the loss.
It appeared that his career with the Serie A giants was set to begin in earnest, but the former Juve man went down untouched during a training session on Thursday afternoon.
Scans revealed he had torn his anterior cruciate ligament, a devastating blow for a player who has ensured such a horrific nightmare with injuries since securing a dream move to Milan.
To add insult to injury, coach Gennaro Gattuso was expected to hand Caldara his league debut on Monday night against Bologna, one day after celebrating his birthday.
The keyhole surgery was carried out by Professor Pier Paolo Mariani with Milan club doctor Mario Brozzi in attendance, the official Rossoneri website describing the operation as a complete success.