The two West Ham players have committed to longer spells in East London, and the club's co-chairman has disclosed that they could remain even longer than reported.
Michail Antonio celebrates with Mark Noble after scoring for West Ham
And he went on to make it clear that both could stay longer than initially reported, as part of their extensions.
Antonio impressed after arriving from Nottingham Forest last summer, going on to make 32 appearances and scoring nine times, and is now signed until 2020.
Cresswell has been a mainstay for the Hammers since arriving two years ago, and has clocked up 89 games for the East London outfit. He has added an extra year to his deal and is committed at the Hammers until 2021.
"I am delighted that we have managed to agree new contracts with Michail Antonio and Aaron Cresswell," Sullivan wrote on whufc.com.
"Both of them are top players and very important to the Club.
West Ham's Aaron Cresswell in action with Swansea City's Leroy Fer
"They have both signed long-term deals and could stay even longer as we have an option after that so that is very good news.
"Michail had to be patient when he first arrived but we all saw his quality when he broke into the team and he scored some crucial goals. He also showed his versatility when he played at right back and will only grow stronger as he prepares for his second season in the Premier League.
"Aaron has also been fantastic for the Club following his arrival from Ipswich back in July 2014. He has gone on to become one of the best left backs in the Premier League and we hope he will continue to show his best form as we make the move into the new Stadium."
The duo represent two of the most successful pieces of business the Hammers have done in recent seasons, with both players coming up from the Championship to effortlessly adjust to life in the Premier League.
West Ham's Aaron Cresswell in action with Tottenham's Kieran Trippier
It is an admirable trait for the Hammers to play a vital step in the progress of young English footballers like both Antonio and Cresswell, and both players found themselves talked about in relation to making the England squad ahead of the European Championships.
It may well have been to the Three Lions' advantage had recently departed England boss Hodgson called on the duo, but as it stands they, alongside the likes of Tottenham's Dele Alli and many of Leicester's Premier League winning squad, are shining examples of why there are bargains to be had in the lower leagues.
West Bromwich Albion's Craig Dawson in action with West Ham United's Michail Antonio