Zeeshan Saeed and Ollie Booth held their nerve for Freiston, Leake and Leverton to seal a low-scoring victory over Welby.
Freiston had dismissed Welby for 55 runs in the South Lincs and Border League Division One, before earning a three-wicket success with a response of 59-7.
With the ball, Tommy Atkinson claimed four top-order wickets to put Freiston firmly on top while Taimur Mian continued his impressive start to the season by picking up another wicket.
Booth claimed four wickets with a spell of impressive pace and accuracy.
However, the tables were turned when Freiston went out to bat, as they were reduced to 11-5.
It was left to Zeeshan Saeed to calm the Freiston nerves with a sensible innings of 21.
Opening bowler Curran claimed his fifth wicket when he trapped Ashok Kumar LBW for eight.
But the arrival of Booth ended proceedings in a quick fashion as he smashed three boundaries in his 15 runs to seal victory for Freiston, who moved into second place in the standings.