**This year’s Under-20 Six Nations has been as hard-fought as ever, with some thrilling contests played out across a disrupted four rounds to date.** Ireland sit top of the table with three wins from as many matches, while each of the sides have shown signs of promise. As ever, the competition is providing the breeding ground for the Guinness Six Nations stars of tomorrow – and prospects at Guinness PRO14 clubs have been at the heart of the action. Here’s a look at the standout players who could be lighting up the Guinness PRO14 in years to come… # **Sam Costelow (Leicester Tigers/Wales)** Costelow may not be a Guinness PRO14 player yet – but he will be from next season. The gifted 19-year-old fly-half has just been snapped up by Scarlets, who he will join from Leicester Tigers over the summer. His performances in the Under-20 Six Nations will no doubt have whetted the appetite of the Scarlets faithful – particularly Costelow’s starring role in Wales’ 23-22 win over England at Kingsholm in Round 4. Costelow scored 18 of his side’s points, including a superb individual try and the dramatic winning drop goal which sealed a famous win for his side. The exciting prospect has been training with Wayne Pivac’s senior Wales squad this season and, if he keeps going at this rate, that may become a more formal arrangement in the not too distant future.