What makes you so sure? Lannan may not be "all that" but he's still here and those "other guys" aren't. There may be guys down there now that can do what Lannan does, but they haven't done it yet, and I don't think Rizzo is going to cut Lannan loose unless/until he's sure he's got a replacement.
This; if, for example, we had assumed that Craig Stammen would just do exactly the same thing as John Lannan, how would that have gone for us? Something about Lannan enables him to sporadically defy the numbers.
I still think we should trade him off if possible - but I wouldn't expect Any Random AAA Starter to produce as he did, though they'd probably be in the same range.