I agree, he made a number of quality 7 inning starts for Detroit last year, before scuffling in June and going on the DL for two months.
More importantly, I think we tend to forget some of the players who from year to year provide "length" out of the Brewers bullpen and are not used in later inning roles:
Hoby Milner: 5.40 era, 1.52 whip, 5.89 FIP over 21.2 innings
Daniel Norris: 6.64 era, 1.57 whip, 6.81 FIP over 20.1 innings
Eric Yardley 6.75era 1.82 whip, 6.81 FIP over 18.1 innings
Angel Perdomo: 6.35era 1.64 whip, 6.11 FIP over 17 innings
Josh Lindblom: 9.72 era, 1.98 whip, 7.37 FIP over 16.2 innings
That's 93 innings of really bad pitching. With Urena I'm sure the floor isn't much worse than a 1.50 whip and a FIP of 5.00, which would be better than they got in the 93 innings above and the ceiling could be much higher.
Its the kind of low cost, no risk move the Brewers should make more of.