Chelsea midfielder Billy Gilmour is facing up to four months after undergoing knee surgery, head coach Frank Lampard has confirmed. Gilmour limped off during Tuesday’s 3-2 win over Crystal Palace following an innocuous collision with Luka Milivojević. The injury comes as a huge blow to the 19-year-old who was just beginning to establish himself, but Lampard is opting to stay positive. “Billy had an operation on his knee, unfortunately, so he’ll be out for somewhere between three and four months,” he told reporters. “I’m obviously very disappointed, we all are and Billy is himself. I spoke with him on Thursday and just offered him some support, really. “He’s a tough boy. It hit him hard – particularly as a young player who’s just made his breakthrough – but it’s part of football and I tried...