Kilmarnock have been credited with an interest in both players, while Aberdeen are also thought to be keen on Hass and Dundee United on Tess.
SportTimes can reveal that Hearts boss Paulo Sergio has enquired about Hasselbaink, who scored eight times for the Buddies last season.
But Sammy has no doubt Lennon will have had plans for replacements in hand.
He said: "Obviously it is disappointing that both players have decided to move on but that is football. But the gaffer sourced both of them and he will have had contingency plans in place to cover for their possible departure.
"Now it has happened I wouldn't imagine Danny would let the grass grow. When you look at his record on signings it has been fantastic, not least with the success he had with Nigel and Jeroen.
"The gaffer also took Darren McGregor from the Second Division with Cowdenbeath and turned him into an established SPL defender. I am sure we can expect him to uncover another couple of gems."
Hugh Murray and Steven Thomson have also left the club, while on their way in are Cowdenbeath skipper Jon Robertson and ex-MK Dons striker Lewis Guy, who signed a pre-contract in January.
But Samson admitted he is sad to see the flying Dutchmen depart and concedes they will be hard acts to follow.
He said: "Nigel started like a whirlwind. He maybe had a bit of a dip in mid-season but he came on strong again towards the end and was unlucky not to finish on a double- figure goal return.
"Tess came here as a trialist no-one had heard of last summer and turned into one of our most consistent per- formers. But that is the way of football – when you do well at one club the vultures circle.
"No-one can dispute the contribution Nigel and Jeroen made to our season. They have been big players for us and will be tough acts to follow.
"But, as I said, the manager has already shown he can spot a quality player and I would back him to do it again over the summer."
"He is determined we will build on our eighth-place finish in the SPL and the two cup quarter-finals and this will not deflect him from that."