I don't think there's much competition. As I said in a previous thread, I think the pitching staff is pretty well set if no injuries. Four starters from last year with Owings. Bullpen same as last year except Rhodes replaces Affeldt. Cordero, Burton, Weathers, Lincoln, Rhodes, Bray. The seventh and last bullpen spot IMO goes to Massett as an innings eater.
The guys looking in from the outside are Ramirez, Fultz, Roenicke, Herrera. If an injury, one of them comes north. Bailey/Maloney/Thompson all headed for AAA.
The starting 8 (actually 9 with platoon) position players are Hernandez, Votto, Phillips, Gonzalez, EE, Dickerson/Gomes, Taveras, Bruce.
That leaves four bench spots. Hairston, Keppinger, Hanigan and one more.
The one more is either Jacques Jones or Ward since the Reds need a lefty bat off the bench.
My guess is that Ward is the presumptive winner due to power as a pinch hitter. Jones on the outside unless there's an outfield injury. Janish/Rosales are around in case of an infield vacancy, such as if Gonzo can't go.
I think that's it, barring another player move. Let me know when it's April.