Riccarton coaching staff want to assess the 18-year-old in an organised friendly after he featured in a bounce match and trained with the first-team during a week-long trial last month.
Nombil is a central midfielder to trade but played wide left as Hearts lost 2-1 to Queen of the South in a closed-door friendly during his stay in Edinburgh. He did enough in training to convince manager Craig Levein that he is worth another look during pre-season.
"I'm trying to get him back in the summer," Levein confirmed to the Evening News. "I really liked him from what I saw. The lad is very young but I want to see him playing in a pre-season friendly.
"He is a central midfielder normally. He is probably a bit more attack-minded than defensive. For a young boy, his training was good."
Obtaining a UK work permit for Nombil could become an issue should Hearts decide to sign him given he has not played any international football. He is currently contracted to Dreams FC in Ghana's Premier League but has spent most of the last year trying to earn a contract in Europe.
A loan move to Czech club Sparta Prague this season was supposed to end in a permanent transfer until visa problems scuppered Nombil's plans. He headed to Sweden in February for a trial with AIK Stockholm before arriving in Edinburgh hoping to earn a contract with Hearts.