This paper analyses the issue of defect nucleation due to fatigue loading in notched components where cracks occur in the proximity of the zone where the major stress gradient occurs. On the basis of recent experimental results where the defects do not nucleate at the notch tip, the effective stress evaluated by means of the implicit gradient approach, can explain the reasons for this apparent discrepancy. Furthermore, in order to find a kind of notch that underlines the nucleation outside the maximum stress zone, rectangular lateral notches have been investigated. Rectangular notches could provide an interesting theoretical and experimental benchmark or reference case in order to validate effective stress definitions. The linear elastic stress field at edges, corners and in the surrounding material of rectangular, sharp or rounded lateral notches has been analysed by means of the implicit gradient approach. The consequent effective values of these notches are evaluated in relation to brittle fractures or their predicted fatigue strength values.