Steven Gerrard's second-half penalty was enough to maintain Liverpool's hold on the Barclays Premier League top spot but how Tony Adams' Portsmouth made them fight.The former Arsenal man's fist game in command after Harry Redknapp's departure ended with nervy Liverpool clinging on to their three points.Gerrard's penalty after Papa Bouba Diop's handling offence after 75 minutes also extended Liverpool's unbeaten start to the campaign to 16 matches.The Liverpool breakthrough came when Sami Hyypia's goalbound header was blocked by Bouba Diop's flailing arms. Referee Steve Tanner booked the Pompey midfielder and pointed to the spot, with Gerrard driving home the penalty.However, Portsmouth created several good chances of their own, including a Younes Kaboul header which went wide. Bouba Diop's first half was not any better than the second following a missed sitter. Lassana Diarra's chip found him, six yards out, but he planted his free header straight into Jose Reina's hands.Liverpool: Reina, Arbeloa, Hyypia, Carragher, Aurelio, Pennant, Alonso, Leiva Lucas, Babel, Gerrard, Kuyt. Subs: Cavalieri, Dossena, Agger, Keane, Riera, Benayoun, Mascherano.Portsmouth: James, Pamarot, Kaboul, Distin, Belhadj, Utaka, Davis, Diop, Diarra, Armand Traore, Crouch. Subs: Ashdown, Kranjcar, Kanu, Hughes, Defoe, Mvuemba, Hreidarsson.