Weiss, on loan from Manchester City, had a hand in both goals in the win at Stoke after stepping off the bench in the second half.
He may be rewarded with a start against Pompey, while Andy O'Brien (thigh), Ricardo Gardner (leg) and Chris Basham (knee) could all be available at the Reebok after shaking off injuries.
Whites (from): Jaaskelainen, Knight, Ricketts, Cahill, Robinson, Muamba, Lee, Gardner, Basham, M Davies, Taylor, Wilshere, Cohen, K Davies, Elmander, Klasnic, Weiss, Al Habsi, Samuel, A O'Brien, Steinsson, Riga.
Source: Team Talk
Source: Team Talk