Mikkola is starting only 27.38% of his 5v5 zone starts in the offensive zone (OZS) this season, which is the lowest in the league. Only two other dmen (100+ mins) have under 30% OZS in the entire league: Scandella, and Andrew Peeke in CBJ. There is only one player in the league under 40% OZS that has a CA60rel under 0 (excellent at preventing shots against) and CF60rel (positive shot impacts for): Erik Cernak from TBL. So, you mostly expect your defensive dmen to get caved in a little bit.
With that in mind, Mikkola has had excellent defensive impacts: 0.68 CA60rel to Parayko's 8.67 and Scandella's 10.04. Only two players in the top 10 fewest OZS have negative CA60rel: Nick Meloche from SJ, and Andrew Peeke (again). Both are righties. Anton Stralman (ARI), Nick Jensen (WSH), and Cernak are the only other 3 below 40% OZS that have negative CA60rel. Mikkola is by far the next closest to being in the negatives. He's been really good 5v5.
With that in mind, let's talk about Chychrun. He's at 44% OZS, and has been having excellent results: -2.56 CA60rel, and 4.00 CF60rel. If he came here, would he be able to replicate that with even fewer OZS than he's been getting in ARI? I'd bet he could. He really is a true #1 LHD in terms of on-ice impacts.
Others that are interesting in the 40-45% range are Adam Pelech (NYI), Ivan Provorov (PHI), and Travis Sanheim (PHI). Everyone else is more or less a lateral move. So, if we are in the market for a LHD, it should between those 3 and Chychrun. My personal preference is Sanheim. But I thought it was important to look at what all of the options are, and really try to do an apples-to-apples comparison for the role we are trying to fill.