LIVERPOOL -- Everton's top scorer Romelu Lukaku only has a "50-50" chance of facing Swansea on Saturday as he battles to recover from a hamstring injury, manager Roberto Martinez says.
Lukaku has hit 18 goals for his club this season but missed last weekend's 1-0 victory over Southampton.
The 21-year-old sustained the injury during a 2-1 win at QPR on March 22 and was forced to pull out of the Belgium squad that beat Cyprus and Israel in Euro 2016 qualifiers during the last international break.
He is still not back in full training, and Martinez is unwilling to risk aggravating the problem.
The manager said: "Romelu Lukaku is the player we need to give as much time as we can before the game on Saturday. I would say at the moment, he's still 50-50. It's an injury we need to make sure is 100 per cent cured before we put him on the pitch.
"At this stage of the season, we need to make sure he's 100 percent well. It's not a major problem. He's been working well over the last two days even though he hasn't joined the group yet."
Martinez has played down concerns about Lukaku's long-term future in recent days, despite reported interest from clubs around Europe.
German media suggested on Thursday that Wolfsburg are looking to buy the striker, who joined Everton from Chelsea for a club-record £28 million in July after a successful season on loan at Goodison Park.
Martinez said last Thursday that he had no concerns over the Belgium international's recent decision to appoint Mino Raiola as his agent.
The manager insisted that he did not see Raiola as a troublemaker, despite the Italian being quoted by Tuttosport in March as saying that Lukaku would be a good signing for Juventus.
Raiola has since told Belgian media that he did not think Lukaku should have joined Everton last summer.
Martinez will look to others to provide the goal threat if Lukaku is not fit on Saturday, but he said he is looking to keep the forward, describing his threat as "unique."
He said: "Romelu is a massive player for us. But in football, you can play in different ways. You need to take that responsibility.
"The goalscoring threat that Rom brings to the side is unique, and we haven't got a like-for-like replacement in that respect, but we've got other players who can be as effective. Arouna Kone is filly fit and starting to be himself. He's shown in the last three games that he's starting to be himself.
"But there are other players who can take the responsibility with Romelu not on the pitch."
Martinez, meanwhile, says he will be "delighted" if midfielder Darron Gibson is fit for the start of next season.
Gibson broke a bone in his foot in training last Friday and is set to miss the remainder of the campaign.
Martinez said: "I don't think we're going to see Darron this season. I'm not too worried about that. My only focus is on making sure that he can recover 100 percent, and get back without any worries over needing extra surgery at the end of it.
"This is a tricky injury, because you've got a little bit of a concern that if you don't heal it properly, then it could come back. That's an area of the foot that's very weak, and we need to make sure that he's fully recovered.
"If we can do that and he can come back in preseason, and be fully fit for the next campaign, I'll be delighted. It's one of those injuries that, if you need to go to surgery, it can become really difficult -- and Darron has been through a lot.
"It's not that he has to come back before the season ends. I want him to be fully fit for the start of next season."
Gibson has suffered a number of injury setbacks since joining Everton from Manchester United in January 2012.
A thigh injury suffered in September that year kept him out for almost three months, before a similar problem that December -- shortly after his comeback -- sidelined him for a further five weeks.
He then suffered cruciate knee ligament damage while on international duty in October 2013, an injury that put him out of action for almost 11 months.
And a separate knee problem, picked up as Republic of Ireland lost to Scotland in a Euro 2016 qualifier in November, kept him out until mid-February.