LONDON, Jan 18 (Reuters) - Arsenal's Brazilian teenager Gabriel Martinelli seized his chance to shine with a goal on Saturday, but Sheffield United earned a 1-1 draw at The Emirates with a strike from John Fleck.The 18-year-old Martinelli, starting in place of suspended frontman Pierre-Emerick Aubameyang, struck from close range late in the first half after a whipped-in cross from Bukayo Saka.Arsenal had a good shout for a penalty when Nicolas Pepe went down in the second half but VAR ruled in favour of the visitors, who then made the most of the let-off.Fleck earned them a point late on when he beat Bernd Leno from close range, and the visitors ended strongly.Sheffield United are seventh on 33 points from 23 games, while Arsenal remain in mid-table with 29 points. (Reporting by Martyn Herman; Editing by Hugh Lawson)