Second-half substitute Thierry Henry netted on his return to the Emirates to send a sluggish Arsenal side into the FA Cup fourth round against a resilient Leeds United outfit.The on-loan New York Red Bulls attacker scored with only his fifth touch since coming on midway through the second period to set up a home clash against fellow Premier League side Aston Villa in the next round.Gunners boss Arsene Wenger handed a number of fringe players the chance to impress with talented youngsters Ignasi Miquel, Francis Coquelin and Alex Oxlade-Chamberlain all named in a strong looking starting lineup.As for the visitors, on-loan Tottenham winger Andros Townsend was given the chance to impress against his parent club’s bitter local rivals, while manager Simon Grayson opted for Argentine striker Luciano Becchio to lead the line.The home side started the match brightly, bossing possession against their Championship opponents, with Russia international Andrey Arshavin squandering a couple of presentable chances early on.Former Sevilla man Sebastien Squillaci came close to breaking the deadlock in the 14th minute. Mikel Arteta played in a wicked set piece which the French defender met with his head, but failed to test Andy Lonergan in the Leeds goal.Leeds finally posed a threat midway through the first half after Arsenal failed to clear a free kick. Mika Vayrynen picked up the loose ball before driving to the by-line. His attempted cross deflected nicely into the path of Becchio who could only smash his close-range effort over.Wenger’s defensive injury problems took another turn for the worse after Coquelin picked up an apparent hamstring injury and was subsequently replaced by debutant Nico Yennaris.Despite continuing to dominate possession Arsenal failed to create another chance and the two sides headed into the half-time interval all square after failing to hit the target.Arsenal opened the second period with greater urgency and finally managed to work Lonergan. Oxlade-Chamberlain surged down the left-hand side before cutting his cross back to Marouane Chamakh. The Moroccan then laid the ball off to Arteta who forced Lonergan into a smart save.With less than 25 minutes remaining, Henry made his much-anticipated comeback as Wenger decided to add the Frenchman and Theo Walcott into the mix as he strived for the win, with the former Barcelona forward's arrival sparking the previously reserved home supporters into a frenzy.The deadlock was finally broken in the 77th minute with Henry capping a dream return to action for the club which helped to turn him into a world star. Alex Song played the ball through to the striker, who took his time before bending a trademark finish past the hapless Lonergan.Leeds almost managed to strike back instantly through a Ross McCormack header which the previously untested Wojciech Szczęsny did well to hold onto. The visitors continued to push for a goal and Szczesny was again called into action by a stinging effort by former Chelsea man Mikael Forssell.With his side safely into the next round, Henry will be hoping his goalscoring cameo will be enough to force himself into contention for a starting berth for the Gunners' Premier League trip to Swansea at the weekend.