West Ham are suffering in the midst of an injury crisis.
Bilic said: “Winston has injured his hamstring in the training session on Wednesday and he will go for a scan on Friday. It doesn't look good. He has done it before and it's one of them, when they tell you four to six weeks. It doesn't look to be a small one. He slipped and he felt it rupture, so it's most definitely a rupture and we're going to see on Friday exactly how long it's going to be.”
Bilic has no further details on the length of the injury, but he is expecting it to be a four to six week absence when Reid has a scan on his hamstring on Friday.
He injured himself in training, and along with the issues with Victor Moses, Manuel Lanzini, Dimitri Payet and Diafra Sakho, the Hammers are in the midst of a potentially season-ending crisis.
All their key players are out of action, and Bilic has made the decision to move training ground at the start of next week to work on better quality pitches.
Having been performing so well this term, all these injuries deal a huge blow to the Hammers heading into the hectic festive period of fixtures, and the East London side will be luck to scrape by with a few wins before the New Year.
On top of the Reid news, Bilic gave an update on Moses’ injury, confirming the winger, on loan from Chelsea, will also be out for up to six weeks.
He said: “Victor is out for four to six weeks.”
Despite all this negative news, Bilic did have one positive update, confirming that Enner Valencia - who has endured an injury hit season - is back in training ahead of the fixture against Stoke City this weekend.
“It's a good thing Valencia is back now and he's training with us today,” Bilic added. “So we'll see if he is in good shape in terms of fitness and in terms of if he is available. He is a great player and we're delighted he is back.”