Spain international Hernandez pulled up with a hamstring strain in the 10th minute of the 3-2 defeat to Manchester City on New Year's Day, and then missed the FA Cup win against Manchester United at Old Trafford.
Belgium's Lamah, who came off the bench to replace Hernandez against City following his injury, is recovering from an abductor strain sustained during a training session, and also missed the cup-tie with Manchester United.
A club statement read: "They could be back in action within two to three weeks, which will bolster Laudrup's options out wide."
Meanwhile, Gwion Edwards and Leroy Lita have returned to the Swans following loan spells at St Johnstone and Brighton.
Edwards featured 17 times for the Scottish Premiership side, scoring once, with the 20-year-old making his debut in their Europa League win over Rosenborg in Norway.
Lita made five appearances for Brighton, with his sole goal coming in a 3-1 Championship victory at Doncaster.
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