The 23-year-old missed last weekend's goalless draw with West Ham due to a stomach complaint similar to the one that kept Ciaran Clark out against Tottenham a fortnight earlier.
However, Delph is likely to be available for the visit of Cardiff as Villa seek a first league win in five matches.
"When you look at the ones we lost against West Ham, Fabian has been fantastic for us," said Lambert.
"He had a bug on Thursday and Friday so that was a blow to see him miss the game at Upton Park.
"I'm pretty sure Fabian's bug is only a short-term kind of thing. He pulled out of training on Thursday. He came in on Friday but he still didn't look the greatest so we sent him home.
"There's been a bug going around. Ciaran had it the other week so hopefully Fabian will be alright for the next game."
Forward Andreas Weimann could face a longer spell on the sidelines after being forced off against West Ham.
"It looks like a hamstring at the minute. I don't know how severe it is," added Lambert.
"The thing is we've got one more game then we get a break so hopefully the break helps him."
'People will remember us because we got to No.1 in the world rankings and achieved great things - but our biggest regret is that we didn’t win anything': Ex-Everton star Kevin Mirallas opens up on 'honour' of being part of nation's golden generation
‘I’m sure we’d have finished in the top four or five if he hadn’t joined Chelsea in January. Him leaving damaged the team, but we couldn’t stand in his way’: Alan Curbishley reflects on failed Champions League dream after selling key player
