Niasse played a give-and-go with Abel Hernandez before slotting the ball under Lukasz Fabianski for the first.
"I'm not happy with the last five minutes to give gifts to the opponent".
"During the January market, we tried to find solutions in the market and Niasse is a different player to the other strikers we have in our squad.
Our shape has been very good, we've been very compact and in the first-half, for the first 20 to 25 minutes, we did frustrate them with our solid defensive shape (but) for the two goals we were much too open".
Speaking to Sky Sports after the game about how he was disappointed with their defensive display, Clement said: "I think that's one game that's got away from us".
"It was our obligation to win this game and it was a very tough one for us".
Swansea - who have lost seven of their last 11 games - remain firmly embroiled in the battle for survival just three points clear of Hull.
Silva brought Niasse off the bench in place of defensive midfielder Alfred N'Diaye and the Senegal striker rewarded him with a brace to fire the Tigers back to within a point of safety.
"I don't think we need 40 points to stay in the Premier League, I think we need 36 or 37 points".
Then he lashed home a bouncing ball which Ahmed Elmohamady had threaded into the box to seal three precious points for his side despite Alfie Mawson's injury time consolation.
Joshua King scored a hat-trick as Bournemouth eased their own relegation fears with a dramatic 3-2 win over West Ham at the Vitality Stadium.
King put Eddie Howe's side in front not long after the break, finishing from close range but Andre Ayew's late equaliser looked to have earned a point for West Ham.
Swansea have also been rejuvenated since changing managers at the start of the year, as they have won five of their eight top-flight games since Paul Clement was appointed as boss.
Martinez's replacement Ronald Koeman liked Niasse even less and he was sent to play with Everton's under-23s.
With the FA Cup quarter-finals taking centre stage this weekend, there are only four Premier League fixtures with Liverpool's home clash against Burnley on Sunday, the pick of the bunch.