Following the appointment of player recruitment guru Tony Henry last year, the Hammers had a seismic shift in their transfer policy with the focus on young hungry players the club could develop.
Indeed the club admitted it wanted, in the main, to bring in players who were no older than 27.
It certainly worked last summer as West Ham pulled off what is considered one of their best transfer windows to date with most of their nine signings performing brilliantly in their debut seasons.
It is a trend they have continued this summer too after Spanish Under 21 international midfielder Pedro Obiang became the first signing under new manager Slaven Bilic.
Obiang impressed as an ever present for Serie A side Sampdoria last season and Sullivan is backing the club's newest recruit to become a 'real superstar'.
"He is a top, top player," Sullivan told West Ham's official website.
“He has played for Spain's Under 21 side and you don't play for them unless you are a good player.
“He has got many qualities that will be admired by the West Ham supporters. We hope that if we can improve him a little bit we could have a real superstar.”
The 23-year-old started his career in his home country with Atletico Madrid before leaving for Sampdoria in 2008 where he has risen through the Italian side's youth ranks into the first team.
He has played 132 times for the Italians scoring four goals, three of which came last season as he really emerged as a fans' favourite.