Rios isn't of an age where you should expect him to be a lost cause. There's a decent chance that he will be an average OF. That has value if you are very thin in the OF. Jimenez is a dandy pitcher in rel life, and he will rack up K's and some wins in fantasy. ERA in Coors and his high-ish WHIP aren't any help.
This is one of those trades that are much closer in fantasy value than they sound in real life. In my league, it would be pretty close for these two. Jimenez has value because good pitchers are spread thin since we have to start so many. But Rios actually grades out with a higher total value for his projected stats this season. His position is pretty deep though.
I'm not saying I'd actually make
the trade, but Rios has a solid chance to be a 20/20 type guy this year, and that has a lot of value if you are weak in OF.
Fantasy baseball is different from real life, and unless your league counts OBP/OPS, batting average, runs, HR, RBI, SB are all that matters. Having a well rounded guy like Rios can have value.
I have Rios in a points based league, and expect him to be slightly above average for my league. In my league, Jimenez has great value because WHIP is not used, and I wouldn't make the trade in a 5 x 5 either, but it certainly isn't such a bad trade offer to even register a blip on "worst trade offers" thread.
It seems I expect a bigger rebound for Rios than the OP does.