Clarke, who watched as his side shipped three goals for the second game in a row, admitted that - despite controlling the majority of the first-half - the performance wasn't good enough as the O's eased to victory.
The Saddlers had taken the lead midway through the first-half as Stuart Sinclair bagged his second goal of the season, but were unable to build upon their lead as the home side struck early in the second-half before going on to extend their lead later in the game.
Goals from Joe Widdowson (48'), Matt Harrold (60'), and Conor Wilkinson (75') were enough to see the home side build upon their recent win over Northamton Town along with adding to the Saddlers' manager's growing list of frustrations.
Clarke, who had already criticised members of his squad for their poor play in the final third, was further disappointed with his backline as individual errors played a major part in the Saddlers' defeat.
Speaking to the assembled media, Darrell said; "Not good enough is it, the second half performance.
"The biggest disappointment for me, we’ve given a sloppy second goal, their left-back has scored a great goal with his right foot, they haven’t really created many opportunities and got us on the counter a little bit.
"But, the biggest thing for me is when you’re in control of a game to really be clinical and finish your chances and we haven’t done that today.
"We haven’t committed the good final ball, we worked opportunities to be ruthless and clinical and we didn’t do that.
"Obviously the goals we conceded, which is unlike us. The last two games you concede six goals in two games and you’re not going to win football matches.
"Three or four of those goals have been individual mistakes. Every goal you can look at two or three things in the build up but we’ve handed them on a plate, so it’s been frustrating, very frustrating second half."