It's possible that this could be Kyle Lohse's (3.49 ERA, 4.30 FIP) last start with the Brewers, though for now it appears he is likely to remain with the team past the trade deadline. The Brewers asking price is rumored to be too high, so unless they come down a bit, we should see Lohse for at least the remainder of 2013.
That's not necessarily a bad thing, of course. The team needs someone to start games, and a number of injuries have already forced their Hand a bit with regards to the rotation. Lohse has also been the best starter the Brewers have had this year, Out of 19 unshortened-by-rain starts, he has 11 quality starts. Since the beginning of June, he has a 2.63 ERA and .625 opponent OPS. Lohse hasn't been quite as good as he was the last two years (mostly due to a much higher HR rate) but he's the best the Brewers have right now.
Lohse has faced four Padres hitters at least ten times. Here is how they have fared:
Sean O'Sullivan (6.43 ERA, 3.33 FIP) has been in the majors off and on since 2009, when he was just 21 years old and playing with the Angels. However, he's never been good enough to stick long term with a career ERA above 6.00 and his best season seeing him post a 5.49 ERA over 19 games, 14 of which were starts.
O'Sullivan has never really been fantastic in the minors, either, posting mediocre numbers and never standing out. He doesn't strike out a lot of people, he doesn't walk a lot of people, he gives up a bunch of hits, his fastball sits at about 89-90 MPH.
O'Sullivan may have advanced too quickly. He started pitching in Triple-A when he was just 21 years old, meaning he was fairly young. For all intents and purposes, he also skipped Double-A, making just three starts there over his career. O'Sullivan is still young (25-years-old) and can certainly get better, but both his major league and minor league numbers indicate he will remain a below average pitcher.
The only current Brewer O'Sullivan has ever faced is Yuniesky Betancourt, who has had two plate appearances against the pitcher with no hits or walks.
For your home Brewers:
For the visiting Padres:
In the bullpen: