Last season, Allen was in solid form and one of our best players until October / November. Lucas returned from his ACL injury, played 2 league games in August and then got injured and was out until early December. By the time he returned, Allen was already in a slump of form and carrying a shoulder injury that needed surgery. Allen's minutes were pretty much reduced from January onwards, relative to the minutes he got while Lucas was out.
Gerrard played 36 league games last season, partnering either Allen (earlier part of the season) or Lucas (from December onwards) mainly. I don't think Lucas and Allen got to play with each other often enough when both were match-fit / injury-free or in decent form to be properly judged as a combination.
I'm looking forward to seeing how the midfield three without Gerrard works out. Three tough away games await them and we'd ideally not have to test the trio against these opponents, but if they pass these tests, we'll emerge with a lot of confidence in the new year to push on.