Clearly, one underrates the value of #3 pitchers. The Sox down the stretch in 2011, and most of last year had a ton of trouble scrounging up #3 starters. A #3 starter (assuming we have the same definition of a #1 starter - there might be 10 of those in the league) can play a decade in the bigs and deliver 180-200 innings. If these guys can get to a #3 level, that'd be success. Frankly, Ranaudo and Barnes probably are looking at that sort of ceiling. Owens has a lot more, but he also is far away from the show and has not actually thrown a ton of strikes - his potential is all projection. Trey Ball is even more projection, but also not eligible to be traded except as a PTBNL. Webster has more probability - although his ceiling is debatable. For a ground ball pitcher he gave up a lot of homeruns in his show starts. But he definitely can be a useful starter. De La Rosa might have more ceiling.
Sox could use another starter - but if you look at their 3-4 record since the break, they have scored a combined 3 runs in the 4 losses. The pitching has been relatively good, just have run into some buzz-saws. Kuroda, Moore, Price and Tillman are 4 of the best in the AL. Not a ton of shame in those losses.