As I just did with Huselius and company, let's do a statistical analysis of the four.
Time On Ice
Naslund: 13:44 EV, 3:35 PP, 0:03 SH
Morrison: 10:57 EV, 3:21 PP, 1:04 SH
Ritchie: 9:09 EV, 0:51 PP, 2:18 SH
Isbister: 10:09 EV, 0:28 PP, 0:11 SH
Morrison is the most well-rounded of the three in terms of role, playing in all situations. Naslund plays the powerplay, while Ritchie plays the penalty-kill in addition to their time at even strength. Isbister recieved practically no time on either special team.
Even Strength- Quality of Competition, GF/GA ON/60 Rates
*Note that quality of competition is ranked among Canucks forwards with 20+ games.
Naslund - T-8th, 2.62GF, 2.62GA
Morrison - 10th, 2.21GF, 2.21GA
Ritchie - T-8th, 1.33GF, 2.37GA
Isbister - 3rd, 1.51GF, 1.94GA
Interesting stuff here. Naslund and Morrison have really dropped off since their glory years- and this despite claims that they're "more defensively responsible". Both just broke even against sub-average competition. Ritchie was even worse off. In fact, looking at this list, the only player I'd be interested in for a role at even strength would be ex-Oiler Brad Isbister.
5-on-4- Points/60, GF/GA On/60 Rates
Naslund: 4.05 PTS, 7.03GF, 0.85GA
Morrison: 6.50 PTS, 7.90GF, 1.39GA
Morrison and Naslund are both clearly still decent options on the powerplay. Morrison actually scored more points (14 to 11) on the powerplay than he did at even strength, while the powerplay as a unit functioned well with either player on it.
Shorthanded- GF/GA On/60 Rates
Morrison: 0.00GF, 2.98GA
Ritchie: 0.76GF, 6.07GA
Morrison, it should be noted, played an injury-shortened season and averaged just over a minute per game killing penalties. Even so, that is an awfully nice PK rate. Ritchie, on the other hand, not so much.
After looking at these statistics we can get an idea of the role each player was in and how successful they were at it. Markus Naslund can still produce at even strength, albeit against softer competition, and is a nice option for the powerplay. His 237 shots probably makes him of interest to the Oilers, but I wouldn't expect him to rebound to his 40-goal days; his shooting percentage peaked at 16.3% in 2003, and has been 10.8% and 10.5% in the last two years. Naslund is likely a player of interest to the Oilers, but it all depends on contract. If he's in the 4M/annum range (as seems likely), he's probably not worth signing.
Brendan Morrison, despite having a reputation as a defensibly reliable presence, was outscored in 2006-07 against middling opponents and just broke even against soft opponents last season. He is, however, an excellent option on special teams, as he's been a reliable producer for the past two seasons. Given his size and the role he plays, Morrison is not a player of interest to the Oilers, but he could be a good signing for someone else.
Byron Ritchie got lit up last season no matter where he played or who he played against. He is not a player of interest to the Oilers.
Brad Isbister was outscored, but not by a lot, against really strong competition, and seems to have found a role as lower-line muscle. Based on last season, he probably deserves a chance at a slightly larger role (expanded role at even strength, penalty-killing duties) and might turn into a nice pickup for whoever signs him. There are a couple of problems, though- a) Isbister didn't impress in a previous stint with the Oilers, b) while he fights, he recorded only 26 hits in 55 games, so he isn't using his size effectively. I don't mind big players who are effective, even if they don't use their size, but when it's a 4th-line guy I get a little pickier in my expectations. Brad Isbister is not a player of interest to the Oilers.