LONDON Chelsea’s interim manager Roberto Di Matteo believes his team are gaining momentum at just the right time as they enter a pivotal period in their season.The Blues’ 4-2 win at Aston Villa on Saturday was their sixth victory in eight matches since Di Matteo took over from Andre Villas-Boas.They gave up a two-goal lead within the space of three minutes late on at Villa Park but showed impressive spirit to hit back and take the points.Chelsea are five points behind fourth placed Tottenham, who beat Swansea on Sunday, have an FA Cup semifinal against Spurs to look forward to and hold a 1-0 lead over Benfica ahead of the second leg of the Champions League quarterfinal on Wednesday.Di Matteo, who was Villas-Boas’ assistant, took over from a far from promising position, but the Italian is pleased with the way his side have picked up their form and he believes they can enjoy a successful end to a troubled campaign."We knew our schedule was difficult but for us it’s just good that we keep this positive momentum and spirit. Every game and win helps us continue and believe,” he said."After they drew level we could have capitulated but you saw the spirit and desire to win the game and reacted in a positive way.However, Di Matteo admits he has fitness concerns over Didier Drogba and David Luiz ahead of Benfica’s midweek visit to Stamford Bridge.Drogba was absent from the squad at Villa Park and Luiz, who has been struggling with an ankle injury, limped off just before halftime. Di Matteo is still unsure whether the pair will be available to face the Portuguese side.