Marcus Smith withstood a battering from Leicester before the England prospect was forced off during the decisive phase of a chaotic Aviva Premiership clash that ended in a 31-28 defeat for Harlequins.
England coach Eddie Jones watched from the stands at Twickenham Stoop as the 18-year-old fly-half who he declared would be polishing George Ford's boot during the coming three-day training camp in Oxford produced another assured performance.
He eventually limped off in the 61st minute after appearing to suffer a muscle injury while taking a restart, placing doubt over his involvement in the pre-autumn camp starting on Sunday, but until that point he had looked sharp, composed and brave as he duelled with Ford.
Leicester initially targeted him, Dan Cole producing the biggest hit on a player Jones sees as a possible World Cup bolter, but both sides' gameplans were ripped apart by a frantic second half that was ultimately decided by two Ford penalties.
At one point in the closing stages of a ragged but exhilarating showdown, Marland Yarde, Mike Brown and Mathew Tait were receiving treatment while the whitewash at both ends came under fierce attack.
Four of the game's five tries were scored in the roller-coaster second half when the coaching teams' role was reduced to ensuring they had a full compliment of players on the pitch as injury took its tool, England flanker Chris Robshaw among those to be stricken.
Smith's first touch was a perfectly-weighted kick into the right corner that when combined with a good chase, forced a penalty from Leicester which Quins' young fly-half sent between the uprights.
Leicester responded with a series of attacking line-outs and after their pack had tested the route one defence, they went wide where an injection of pace from Jonny May and the lurking presence of Nick Malouf caused enough doubt in home minds for Telusa Veainu to slide over.
Once Smith and Ford had swapped penalties the Tigers entered half-time 11-9 ahead, but the pendulum swung decisively in the space of two minutes after the interval with number eight Mat Luamanu central in both of Quins try.
Leicester's scrum fell apart and Luamanu led the breakaway by the back row and Danny Care that only ended when Ellis Genge caught the ball in an offside position. Genge was lucky to escape the sin-bin but Quins could at least count on the quick wits of Care, who darted over the whitewash from close range to touch down.
A poor pass from Ford launched the counter-attack that led to Leicester being breached for a third time, but it also took sharp reflexes from Smith and support work from Yarde to create the chance for Luamanu, who just had the legs to crash over.
Just as it looked as though Quins were out of sight, it became the Tigers' turn to cross twice in two minutes. The vision and passing of Matt Toomua engineered the first for May, who easily outpaced England rival Yarde to cross, before Greg Bateman bullocked through an increasing ragged home defence.
More twists and turns in an unpredictable match were to come, the first arriving when Alofa Alofa ran on to Care's pass to cross under the posts but the most decisive being the two Ford penalties that settled a crazy afternoon.