It doesn't make sense to start Lucas no matter which way you come at it.
The whole idea is not to telegraph the underlying basis of one's entire analysis this "loudly".
As ElstonGunn said: "I will say that Lucas was actually perfectly fine for the first 45 minutes."
Furthermore, he didn't "give the ball away a number of times" in the 2nd half. He gave the ball away twice. Once on an attempted soft pass to Skrtel (unclear what the effect of the wind had on that, or what part of the responsibility for the pass not reaching its destination falls on the intended receiver, Skrtel) and once on an attempted pass to Coutinho which was partly shielded by the referee (it should thus probably not been attempted) and smartly cut-off and intercepted by Wanyama. That's it for the 2nd half.
Lucas and Gerrard found themselves and appeared to have been instructed to find themselves on the same horizontal line a lot in the first half, much less so in the 2nd half (until, of course, Allen came in for Lucas). The CBs did not spead out as wide as in the 4123. Moreover, it wasn't a matter of one of Lucas and Gerrard 'rotating' into the '1' spot with the other being a 'cautious' box2box (following, perhaps BR's motto "if you can't reliably run back, do not run forward") as was the case in the beginning of the 2nd half. Assuming that SFC were set up (and were able to execute) to prevent Gerrard and Lucas from being an 'organizing/controlling' duo and effecting either vertical passes to checking forwards (the front 4, the 3-1 part of the formation) or longer diagonal passes to the advancing fullbacks, the onus for doing so would fall on the CBs, especially Lovren, with his more refined footballing skills and two-footed full passing repertoire. The latter obliged much more so than Skrtel. The end result though, whether due to 'not quite right' pass delivery (less likely) or due to persistently mediocre showing for the ball, shielding, pass-reception and 'getting turned' by Coutinho, Sturridge, Johnson, Sterling, Henderson and Manquillo (in that order), was not so good.
Having said, the times, especially Gerrard attempted some fine longer passes to all of the above, it was mostly the latter's 'fault' that they didn't work out, rather than Gerrard's. Lucas's forward passes were invariably successful, although less 'promising'. It must also be noted that Lucas did a lot more 'compressing' of the lines and pressing/marking, dispossessing in the opposition half and re-starting the attack than Gerrard.
Coutinho was not starved for service. He was marked extremely well (with a little help from Mr. Clattenburg who either allowed plenty of manhandling to go unpunished completely or applied his peculiar and to me erroneous understanding of the 'advantage' rule, such that mere retention of possession subsequent to a clear, blatant foul on one of our players on our part was adjudged as constituting "advantage" for us) AND he had "one of those days", where practically nothing that normally 'works' did. Even so, he had a few moments of brilliance or, at the very least, almost brilliance.
Sturridge, apart from his well-taken goal, was frustratingly ineffective, on multiple levels. Again, the referee did him no favors. Furthermore, he was uncharacteristically 'selfish' (see what I did there?) on the break or counter, holding on the ball too long instead of feeding open teammates busting guts especially on the flanks.
We got done in with the use of one of the plays that PoP diagrammed for us in the pre-match thread (frighteningly prescient post, btw), with Lucas leading the way of culpability in a cascade of defensive errors that certainly helped out SFC players. In the second half, and with Lucas no longer on the pitch, we almost got done in AGAIN through the use of the same play (71st/72nd minute, Clyne involved again as the full-back third runner) with Gerrard leading the way of culpability of defensive errors, followed uncharacteristically by Lovren.
Manquillo was tested repeatedly and was not found wanting. In fact, he came through with flying colors, especially in comparison to his much more senior counterpart playing wrong-footed on the other flank. I shall say nothing more about Glen Johnson given my well-known negative bias towards him.
Skrtel was very good defensively (bar a couple of hard-to-explain misjudgments of the flight of the ball or the bounce), although not always quick enough to follow Lovren's lead and stepping up.
Lovren was excellent defensively, with one exception (which wasn't costly, in the end).
Henderson and Sterling's performances have been more than adequately described and analyzed above.
Mignolet: Excellent shot-stopping, improved dealing with crosses (still, not exactly excellent) and, sorry, mediocre longer-ball distribution. No, I am not expecting him to be Pirlo, Xabi and Gerrard combined in his longer passing, btw.
Allen and Lambert contributed properly and were good substitutions.