The fullback is a target for Roma.
Lampard said, "That's not clear yet. Zappacosta is our player. Reece [James] is injured and will potentially be another two or three weeks until he's back. That's a decision that will be made as we go on.
"I've been really impressed with Zappacosta's attitude and quality and how he's trained. He's a very good player. We have to make sure we are happy with the squad when the European window shuts.
"It'll be a decision for us and Zappa. I want players happy. The professionalism he has shown since he has been here has been great. It will be an ongoing conversation but he's our player."