Town will be without Kane Vincent-Young, James Norwood and Kayden Jackson for Saturday’s season-opening Carabao Cup tie against Bristol Rovers at Portman Road.
Norwood made his first appearance of the summer as a half-time sub in last week’s 1-0 loss at Cambridge United having spent much of pre-season continuing his rehabilitation from the groin operation he underwent in January.
Lambert says the 29-year-old has suffered another minor problem and won’t be involved against the Gas.
"James has been injured, he’s just getting back to fitness at the minute,” he said. "He had a little strain on his hip the other day.
"I think this game will be too early for him. As I said before, there are two cup games before the league actually starts next Sunday.”
Asked whether Norwood, who is understood to be interesting Dundee United and Swindon will remain a Town player, Lambert added: "James in my opinion will be here.”
Reflecting further on players currently on the sidelines, he added: "We’ve still got one or two injuries. I can’t risk them at the minute.
"We’ve got two cup games before the league starts. I’ll take a bit of caution with guys who are carrying little knocks and if they’re not ready then I won’t take the risk.”
Also missing out on Saturday are right-back Kane Vincent-Young (achilles) - "No, not fit” - and striker Kayden Jackson (groin) - "Not fit”.
Winger Gwion Edwards, who has been suffering with a groin? problem could be involved: "I’ll see how he is this morning.”
Left-back Myles Kenlock, who has had a thigh issue, is in a similar position - "See how he is this morning” - and Janoi Donacien, who picked up a knock at Cambridge last week, is also improving: "He’s doing better, we’ll see how he is as well.”
Midfielder Cole Skuse was expected to be back in training earlier in the week after a minor knee problem.
Also missing are forward Armando Dobra and keeper Adam Pryzbek as they're away on international duty with the Albania and Wales U21s respectively.
Dobra might well have been in with a shout of involvement either on Saturday or against Arsenal's U21s in the EFL Trophy on Tuesday.
"He’s got the national games, it’s good for him to get a couple of games under his belt,” Lambert added regarding the 19-year-old.
Tristan Nydam is expected back in October, while Ben Morris is again sidelined long term having recently suffered another ACL injury.