The Champions League  clash between two of the highest-scoring sides — Barcelona  and Manchester City  — in Europe is arguably the tie of the last 16 round and Gerardo Martino thinks possession could be the key given both sides' attacking instincts Barcelona Football Club boss Gerardo Martino believes the first leg of his side's Champions League last-16 tie against Manchester City on Tuesday comes at the right time as he has a fully-fit squad to choose from. The Catalans maintained their place atop La Liga on goal difference with a 6-0 thrashing of Rayo Vallecano at the Camp Nou on Saturday. Lionel Messi continued his fine form with a double to move past Real Madrid legend Alfredo di Stefano as La Liga's third highest goalscorer of all time on 228. There was a further bonus for Martino's men as Neymar made his return after three weeks out with a sprained ankle and the Brazilian forward made an instant impact as he smashed home his side's sixth goal of the evening from 25 yards. "We come into the match in very good form," said Martino. "It is probably the best moment we could have hoped for to face the challenge of the last 16 of the Champions League, independent of the opponent we face. "Especially physically, it is a bonus to have everyone available and in very good shape." The clash between two of the highest-scoring sides in Europe is arguably the tie of the round and Martino thinks possession could be the key given both sides attacking instincts. "Both teams defend themselves with the ball, so whoever manages the ball better will have more chances to win. In this sense both teams are quite similar, they always try be proactive. "If we can keep the ball for more time then we will reduce the chances they have and give ourselves a better opportunity." On top of Messi and Neymar's comeback from injury, Barca's upturn in recent weeks has directly correlated with Andres Iniesta's return to form. Iniesta and Cesc Fabregas shone in midfield as they tore the Rayo defence to shreds on Saturday and Martino admitted he has a big decision to make over who starts in midfield at the Etihad having rested Xavi Hernandez. "Andres finished the season last year very well, I remember his game against Getafe (in December) that was exceptional. "He then got a knock against Atletico Madrid which kept him out for 10 days and affected him quite a bit. "The truth is that when Andres plays well the team plays differently. He manages everything well, he has played three very good games on the bounce, but nothing out of the ordinary to what he does season in, season out. "It is very difficult to pick a team every three days when all the players are available because any decision that you take can be unjust against someone. "However, it is clear that Barcelona is such a big institution, that plays in so many competitions, that we have to have a squad capable of dealing with that. "I am paid to make decisions and pick who will play."