Manager Eric Wedge acknowledged the team didn't want to eliminate any options before it had to with games still remaining.
"What we're trying to do is give ourselves a little more time," Wedge said. "When you talk about the end of Spring Training, you want to protect yourself against so many different things, one of which is injury, quite frankly.
"If you don't have to make a decision early, you try not to do it. Jack and I did have conversations with both of them. Not all decisions have been made and we told them that and that's where we are. I'd like to tell them more, but we've got to play this out and do what's best for the ballclub, manage the roster accordingly and go from there."
Wells is out of Minor League options, so he would either need to be released or traded if the team settles on Bay.
One overhanging issue is the question of center fielder Franklin Gutierrez's health. Gutierrez played just 40 games last year because of injuries and has been slowed the last few weeks by tightness in his legs, though he played the past two days before getting an off-day on Thursday.
If Gutierrez is out, Michael Saunders moves to center field and then the corner spots fall to Michael Morse, Raul Ibanez and whichever of the two outfielders the club decides to keep.
"It's a consideration," Wedge said of Gutierrez's situation. "Obviously we've slow-played him and I'll continue to make sure we take care of him, especially early in the season. He's going to get days off. We're a better ballclub when he's in there, but if he's not an option for us it doesn't do us any good."
Wells is more of a center field option, though Bay has played there a little. The club signed veteran Endy Chavez to a Minor League deal last week to provide more depth as well. Chavez is still with the team, along with several other players that will be sent down to the Minors after Saturday's game.
Bay has had a strong spring, batting .320 with two home runs and six RBIs in 50 at-bats. Wells has hit .189 with two home runs and 14 RBIs in 53 at-bats. Wells is the better defender, but Bay has proven capable there as well this spring.