Lukaku left Chelsea in 2014 to secure a permanent move to Everton.
Zlatan Ibrahimovic signed on a free transfer from Paris Saint-Germain.
Lois Karius started in each of Liverpool's five pre-season friendlies.
The Czech Republic international insists that building a chemistry is equally important.
Jurgen Klopp has made six signings thus far in the window.
Gabriel Jesus has scored 19 goals in 31 appearances for Palmeiras.
Dutch striker looks set to leave Fenerbahce this summer, just a year after joining from Manchester United.
Tottenham have made two signings thus far this summer.
Oguzhan Ozyakup is an Arsenal youth academy product.
Gazidis says it is difficult to compete as increased financial power has allowed lower clubs to bid for top targets.
Alexandre Lacazette has scored 23 goals last season and 31 the year before.
Mane has scored 11 and assisted 6 in 37 appearances for Southampton last season.
Arsenal are currently in the US where they will play San Jose on Thursday, 28 August.
The Gunners have made three signings thus far in the transfer window.
Mertesacker was part of their first pre-season game against Lens.
Jamie Vardy scored 24 goals for Leicester in the league last season.
The Reds have made six signings so far.
Arsenal have made three signings thus far this season.
Brad Smith made 10 appearances for Liverpool last season.
Jose Mourinho has designs to sign Paul Pogba this summer.
Riyad Mahrez was involved in 28 goals for Leicester City last season.
Manchester United have already signed three players this summer.