Two different shapes of match here, and in both the side with the heavier pre-match facts is clear. One is a table-topper visiting a team near the bottom that rarely gets shots on target. The other is a home side with an excellent home record facing a visitor whose attack is down to one natural forward.
Wrexham against Middlesbrough: Boro are first in the table, Wrexham nineteenth. Over the last ten Boro average about twenty shots with over seven on target and a chance quality well above Wrexham, who manage under three shots on target and around one goal per game. Wrexham are also without their left-back, a forward and a midfielder, and those players had already missed recent games, so the poor form is real and not a surprise. Boro should hold the ball, win corners and keep coming. The Cardiff draw, where they wasted a mountain of chances, is the warning, but the gap in shot quality is too large to ignore. That's why I'm siding with Middlesbrough to win.
Rennes against Olympiacos: Rennes have lost twice recently and their defence has leaked, so this is not a clean picture, but at home they have won eight of nine. Olympiacos arrive with their main striker injured and others off the roster, a thinner midfield, and three games in ten days. Their wins are tight, 1-0 and 2-0 type results, so a draw is a live outcome. That's why I'm siding with Rennes at home not to lose.