Perth Glory coach Tony Popovic has a headache -- and he wouldn't want it any other way.
Popovic has some big selection calls to make ahead of Sunday's A-League match against Central Coast, with Diego Castro the biggest of the lot.
Castro hasn't played since injuring his hamstring during the preseason, but the veteran is now back in full training and pushing for selection against the Mariners at nib Stadium.
Veteran striker Brendon Santalab (hamstring) is also available to play his first game of the season, while centre-back Tomislav Mrcela will be hoping to slot straight back in after serving a one-match suspension.
Glory sit on top of the ladder with three wins and one draw, but Popovic said he wouldn't be afraid to change an unbeaten side if he saw the need for it.
Popovic wants to put Castro through his paces on Saturday before making a final decision on the 36-year-old.
"I'm just weighing up where he's at physically," Popovic said. "The last 10 days he's been training with the team, doing all the sessions with the group.
"We want to make sure that if we do use Diego, he will make a difference.
"But we also don't want to throw him in there for the sake of one match if he's not ready."
Socceroos defender Matthew Spiranovic will miss at least another match as he continues his long recovery from hip surgery.
Santalab is likely to have to bide his time on the bench given the hot form of striker Andy Keogh, who has scored four goals in four games.
Central defender Dino Djulbic performed well in the 2-0 win over Adelaide, but he could be forced straight out given that Mrcela is available to return.
"It's a great headache," Popovic said of his selection options.
The last-placed Mariners will be without star midfielder Tommy Oar, who strained a knee in the 4-1 loss to Melbourne Victory.
However, veteran striker Matt Simon is available to play after recovering from injury.
The Mariners have just two points to show from their opening four games, and will be desperate to post a win in Perth.