Davies picked up a slight knee injury in the defeat to Wigan last weekend and will not be risked, while Tyrone Mears has suffered a setback with his recovery and is facing another six weeks on the sidelines.
Coyle has confirmed he will field a strong side for the FA Cup clash at the Den with Ream and Miyaichi both set to play, while Dedryck Boyata and Tuncay could also figure in the starting XI.
New striker Marvin Sordell is back fit but cannot play as he figured for Watford when they took on Tottenham in the fourth round, so Ivan Klasnic could get the nod in attack.
Meanwhile, Coyle remains upbeat going into the game despite two poor results against Norwich and Wigan.
"What we have always done is remain balanced," Coyle said in his pre-match press conference. "When we beat Liverpool, we didn't think we were Barcelona and equally, because we have lost the game last week, we are not going to think we are a poor side.
"We had a bad day at the office, but we have to pick ourselves up, ready to go again, and the FA Cup tie at Millwall gives us a chance to do that and show our quality."