In addition to his goals and assists, his unquestionable value to the team can be seen in the fact that in the two games he has started on the bench, Barca were trailing until their talisman came on and helped rescue them.
La Liga top scorer Lionel Messi struck a hat-trick for the runaway leaders.
Leganes failed to provide any real attacking threat in the remaining stages of the second half as Barca went into the break leading by two goals.
Lionel Messi's fitness has been cause for concern after the forward missed Argentina's worldwide friendlies because of a hamstring tweak.
In comparison to recent versions of this fixture, which have included Champions League finals, Cope del Rey finals and league games with both sides vying for the championship, this at times had a rather low-key feel.
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The Hammers last won at Stamford Bridge in September 2002 when Paolo Di Canio's late goal clinched a 3-2 victory. Chelsea head into the match having lost three of their last four fixtures in the top flight.
Second half staminaBarcelona have fallen behind eight times in the league this season but fought back to draw against Atletico Madrid, Valencia, Espanyol and Sevilla, while they rallied from a losing position to beat Real Sociedad, Getafe, Girona and Alaves. "It has been quite hard, because of the fact it's an old record that hasn't been broken for a long time".
Sevilla, who also scored an own goal in their midweek Champions League defeat to Bayern Munich and have now lost four of their last five matches, nearly levelled things up three minutes before the break but Sandro Ramirez's volley was kept out by goalkeeper Sergio.
Valverde says Saturday's game is the only focus, though, with five more wins all that is needed for Barcelona to wrap up their third league title in four years.
"The game has brought us three very important points".
His mood will have lifted in the wake of his latest display, with Gomes helping to cover the absence of World Cup victor Sergio Busquets in the heart of Barcelona's midfield.