Robbie did the damage to his left knee in the closing minutes of Tuesday night's 2-1 victory over Middlesbrough having come off the bench a matter of minutes earlier and hammered home the winning goal.
Meanwhile, JJ picked up a knock to his ankle in the derby at Arsenal on Saturday, bad luck for the midfielder having just returned from a calf injury.
Martin said on Thursday afternoon: "Robbie has a medial ligament strain and will be out for fve to six weeks, although hopefully he'll return a bit earlier because he's a quick healer.
"JJ took a blow to his ankle and he'll probably be out for four weeks. That's a blow for him as well."
We'll have full team news on Friday...
Martin Jol reports that Robbie Keane could be sidelined for up to six weeks with medial ligament damage - Jermaine Jenas also faces a month out.