Peterborough United failed to score for the third game in a row as they were held to a 0-0 draw by Walsall at the ABAX Stadium.
Marcus Maddison struck an early free-kick into the wall after Bostwick was upended 30-yards from goal while striker Luke James, restored to the line-up, headed wide from a long Michael Smith throw in.
Jordan Cook sent a curler from 20-yards inches past the post for the visitors on nine minutes. Alnwick denied Hiwula with a routine stop before Posh cut the visitors open.
Bostwick slid a perfect ball into the path of the onrushing Norris and his shot was beaten away by O'Donnell. Michael Cain volleyed over from a corner kick on 24 minutes as the Saddlers pressed for the breakthrough.
Cain was desperately close to scoring on 27 minutes after a fine piece of individual skill created the chance on the volley, his effort going just past the post.
The influential Cain side-footed wide following a swift counter-attack on 33 minutes as Posh were wide open at the back. An intelligent throw out from Alnwick set Posh on the counter attack on 41 minutes, but James cross just eluded Mclean in the box.
Maddison forced O'Donnell to tip his cross-shot around the post three minutes after the re-start as Posh made a bright start to the second half. Bostwick was cautioned for a foul on 49 minutes.
Cain sent a dipping free-kick just past the post from the resulting set-piece although Alnwick was confident that the shot was going wide.
Mclean fired over on 56 minutes from 30-yards after a neat lay-off from Norris. Smith made a fine tackle at the other end to bring to a conclusion a mazy Chambers run into the box.
Conor Washington replaced Mclean on 63 minutes as Dave Robertson made another change. Maddison saw a dipping free-kick gathered by O'Donnell moments later.
Anderson headed wide from a deep Zakuani cross on 71 minutes as Posh tried to find the opening goal in this contest. On 75 minutes, Anderson saw a fierce shot beaten away at the near post by O'Donnell.
Joe Newell replaced Maddison on 77 minutes as Robertson made his final switch of the afternoon. Cook was denied at the near post by Alnwick after wriggling into the box as the game moved into the final 10 minutes.
Cain sent a dipping volley inches past the post while James was denied by O'Donnell at the other end. As the game moved to it's conclusion, James saw a shot beaten away by O'Donnell before a Newell cross was cleared.
Full-time: Peterborough United 0-0 Walsall
Posh: Alnwick, Smith, Ntlhe, Bostwick, Zakuani, Taylor (sub Anderson 46min), Payne, James, Mclean (sub Washington 63min), Norris, Maddison (sub Newell 77min) . Unused subs: Henry, Brisley, Oztumer, Santos.
Walsall: O'Donnell, Purkiss, Taylor, O'Connor, Chambers, Sawyers (sub Mantom 68min), Cain, Morris, Cook (sub Bakayoko 86min), Hiwula (sub Forde 68min). Unused subs: MacGillivray, Downing, Kinsella, Grimes.
Attendance: 6,711 (210 Walsall fans).