As far as Bonderman is concerned, he has missed the last two seasons and the better part of three of the last four seasons. Because of the layoff, Bonderman's chance of regaining his top form are much less probable than Garland.
Garland has a career record of 132-119 with a 4.32 ERA in 353 games, 330 starts. Most of his time was spent with the Chicago White Sox (from 2000-2007) as he has also pitched for both Los Angeles teams, Arizona and San Diego. Though Garland pitched a couple of big postseason games for the White Sox in 2005, he failed to either make the postseason roster or appear in a game in the 2000, 2008 and 2009 postseasons for the White Sox, Angels and Dodgers, respectively. However, he did throw a complete game victory in game three of the ALCS against the Angels and 7 solid innings in his start in the following World Series.
Two former MLB pitchers, in my opinion, compare the most to Garland and his track record. Of course, it is very difficult comparing one generation to the next, as the game of pitching has changed dramatically. Kevin Gross finished with a 142-158 record, pitching on several teams that were not that good throughout his career. He had a 4.11 ERA and appeared in 474 games, 368 of them as a starter. San Diego Padres manager Bud Black pitched over 200 innings in five seasons, but was used for a couple of seasons as a reliever and spot starter. His career line was 121-116, 3.84 in 398 games, 296 starts. Though Garland has not been a relief pitcher throughtout his career, he may need to spend some time in a MLB bullpen like Gross and Black did. I am sure the Mariners would like Garland, Bonderman and Joe Saunders to pitch a lot of innings this season, allowing their younger pitchers to develop in the minor league. Kevin Millwood and Jason Vargas did a very good job last season of keeping the team in a lot of games.
Black was a mainstay in the 1984 and 1985 Kansas City Royals rotations that made the postseason. He took a loss in of the games of the 1984 ALCS against Detroit, but pitched very well in the 1985 ALCS against Toronto. He would then take the loss in his only start in the 1985 World Series against St Louis. The most interesting similarities between Garland and Black are the amount of postseasons both pitchers missed out on. Black missed his during the end of his career. He was 8-2 on the 1993 San Francisco Giants team that won 103 games but managed to miss the playoffs. He was also on the 1995 Cleveland Indians team that won the AL Pennant, but was not on the postseason roster. Also making an appearance for the Indians that season was none other than current Boston Red Sox manager John Farrell, also his teammate with the Indians during the 1988 and 1989 seasons.