Mthembu is currently training with Celtic, after the club again expressed their interest in luring the former Orlando Pirates frontman to Manguang.
Despite being with the club for more than a week, co-coach John Maduka says the club will further assess him during a friendly match against the Crocodiles at Siwelele Park this afternoon.
"Mthembu is coming alright," Maduka tells KickOff.com. "But we are playing a friendly this afternoon against the senior national team of Lesotho, and we will also give him an opportunity [to impress]."
Maduka further explained that Mthembu's match fitness is one area of uncertainty, after he failed to make a single appearance for Amakhosi since March last season.
"You must remember that as much as he was registered at Kaizer Chiefs, he was not playing," he adds. "But we'll see after today and then before the end of next week we will make a decision."
The former Celtic midfield stalwart also says the club are not interested in making further changes to their squad, but are only looking to strengthen their options up front.
"It's only up front where we are trying to strengthen, that's the reason we are only looking at Mthembu.
"We don't want to destabilise the team by making changes in every position. It's not like we've been playing badly, it's just that we've been unlucky in front of goals," he says.
Celtic are set to kick-off the new year with a clash against African champions Mamelodi Sundowns on February 8, and have until January 31 to snap up Mthembu.